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{{Tobacco}}
{{Tobacco}}

The '''health effects of tobacco''' are the circumstances, mechanisms, and factors of tobacco consumption on human health. Epidemiological research have been focused primarily on [[tobacco smoking]],<ref name="WHOPrevalenceAdultsAge15" /> which has been studied more extensively than any other form of consumption.<ref name="WHOMayoReport" />
The '''health effects of tobacco''' are the circumstances, mechanisms, and factors of tobacco consumption on human health. Epidemiological research have been focused primarily on [[tobacco smoking]],<ref name="WHOPrevalenceAdultsAge15" /> which has been studied more extensively than any other form of consumption.<ref name="WHOMayoReport" />


Tobacco use leads most commonly to diseases affecting the heart and lungs, with smoking being a major risk factor for [[myocardial infarction|heart attacks]], [[stroke]]s, [[chronic obstructive pulmonary disease]] (COPD), [[emphysema]], and [[cancer]] (particularly [[lung cancer]], [[Cancer of the larynx|cancers of the larynx and mouth]], and [[pancreatic cancer]]). It also causes myocardial infarctions, peripheral vascular disease and hypertension, all developed due to the exposure time and the level of dosage of tobacco. Furthermore, the earlier and the higher level of tar content in the tobacco filled cigarettes causes the greater risk of these diseases. Due to higher levels of tar content in third world countries, people who smoke in third world countries are more vulnerable to diseases. Poorer nations also lack the inclusion of filters that richer nations have, however the mortality rate does not show a significant decrease due to filters as many people, filter or no filter, die due to the main reason being their addiction and intake of tobacco.<ref> Nichter, M., and E. Cartwright. 1991. Saving the children for the tobacco industry. Medical Anthropology Quarterly 5 (3):236-256.</ref>
Tobacco use leads most commonly to diseases affecting the heart and lungs, with smoking being a major risk factor for [[myocardial infarction|heart attacks]], [[stroke]]s, [[chronic obstructive pulmonary disease]] (COPD), [[emphysema]], and [[cancer]] (particularly [[lung cancer]], [[Cancer of the larynx|cancers of the larynx and mouth]], and [[pancreatic cancer]]). It also causes myocardial infarctions, peripheral vascular disease and hypertension, all developed due to the exposure time and the level of dosage of tobacco. Furthermore, the earlier and the higher level of tar content in the tobacco filled cigarettes causes the greater risk of these diseases. Due to higher levels of tar content in third world countries, people who smoke in third world countries are more vulnerable to diseases. Poorer nations also lack the inclusion of filters that richer nations have, however the mortality rate does not show a significant decrease due to filters as many people, filter or no filter, die due to the main reason being their addiction and intake of tobacco.<ref>Nichter, M., and E. Cartwright. 1991. Saving the children for the tobacco industry. Medical Anthropology Quarterly 5 (3):236-256.</ref>


The [[World Health Organization]] estimate that tobacco caused 5.4 million deaths in 2004<ref name="WHO">[http://www.who.int/entity/healthinfo/global_burden_disease/GBD_report_2004update_full.pdf WHO global burden of like ftw!disease report 2008]</ref> and 100 million deaths over the course of the 20th century.<ref name=WHO2>[http://www.who.int/entity/tobacco/mpower/mpower_report_prevalence_data_2008.pdf WHO Report on the Global Tobacco Epidemic, 2008]</ref> Similarly, the United States [[Centers for Disease Control and Prevention]] describes tobacco use as "the single most important preventable risk to human health in developed countries and an important cause of premature death worldwide."<ref name="fn1">"[http://www.cdc.gov/tobacco/quit_smoking/you_can_quit/nicotine.htm Nicotine: A Powerful Addiction]." Centers for Disease Control and Prevention.</ref>
The [[World Health Organization]] estimate that tobacco caused 5.4 million deaths in 2004<ref name="WHO">[http://www.who.int/entity/healthinfo/global_burden_disease/GBD_report_2004update_full.pdf WHO global burden of like ftw!disease report 2008]</ref> and 100 million deaths over the course of the 20th century.<ref name=WHO2>[http://www.who.int/entity/tobacco/mpower/mpower_report_prevalence_data_2008.pdf WHO Report on the Global Tobacco Epidemic, 2008]</ref> Similarly, the United States [[Centers for Disease Control and Prevention]] describes tobacco use as "the single most important preventable risk to human health in developed countries and an important cause of premature death worldwide."<ref name="fn1">"[http://www.cdc.gov/tobacco/quit_smoking/you_can_quit/nicotine.htm Nicotine: A Powerful Addiction]." Centers for Disease Control and Prevention.</ref>


Smoke contains several carcinogenic pyrolytic products that bind to DNA and cause many genetic mutations. There are over 19 known chemical carcinogens in cigarette smoke. Tobacco also contains [[nicotine]], which is a highly addictive psychoactive chemical. When tobacco is smoked, nicotine causes physical and psychological dependency. Tobacco use is a significant factor in miscarriages among pregnant smokers, it contributes to a number of other threats to the health of the fetus such as premature births and low birth weight and increases by 1.4 to 3 times the chance for Sudden Infant Death Syndrome (SIDS).<ref name="SurgeonGeneralPassiveSmoking2006">{{cite web|url=http://www.surgeongeneral.gov/library/secondhandsmoke/report/fullreport.pdf|title=The health consequences of involuntary exposure to tobacco smoke: a report of the Surgeon General|accessdate=2009-02-15|year=2006|format=PDF|publisher=U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health|location=Atlanta, U.S., page 93}}</ref> The result of scientific studies done in neonatal rats seems to indicate that exposure to cigarette smoke in the womb may reduce the fetal brain's ability to recognize [[Hypoxia (medical)|hypoxic]] conditions, thus increasing the chance of accidental [[asphyxia]]tion.<ref>{{cite journal|author=Pendlebury JD, Wilson RJ, Bano S, Lumb KJ, Schneider JM, Hasan SU|title=Respiratory control in neonatal rats exposed to prenatal cigarette smoke|journal=Am J Respir Crit Care Med|volume=177|issue=11|pages=1255–61|year=2008|month=March|pmid=18310476|doi=10.1164/rccm.200711-1739OC}}</ref> Incidence of [[impotence]] is approximately 85 percent higher in male smokers compared to non-smokers,<ref name="tobaccoprogram.org">{{cite web|title=The Tobacco Reference Guide|url=http://www.tobaccoprogram.org/tobaccorefguide/ch12/ch12p1.htm|accessdate=2006-07-15}}</ref> and it is a key cause of erectile dysfunction (ED).<ref name="tobaccoprogram.org"/><ref name=pmid15924009>{{cite journal|author=Peate I|title=The effects of smoking on the reproductive health of men|journal=Br J Nurs|volume=14|issue=7|pages=362–6|year=2005|pmid=15924009}}</ref><ref name=pmid15146084>{{cite journal|author=Korenman SG|title=Epidemiology of erectile dysfunction|journal=Endocrine|volume=23|issue=2-3|pages=87–91|year=2004|pmid=15146084|doi=10.1385/ENDO:23:2-3:087}}</ref>
Smoke contains several carcinogenic pyrolytic products that bind to DNA and cause many genetic mutations. There are over 19 known chemical carcinogens in cigarette smoke. Tobacco also contains [[nicotine]], which is a highly addictive psychoactive chemical. When tobacco is smoked, nicotine causes physical and psychological dependency. Tobacco use is a significant factor in miscarriages among pregnant smokers, it contributes to a number of other threats to the health of the fetus such as premature births and low birth weight and increases by 1.4 to 3 times the chance for Sudden Infant Death Syndrome (SIDS).<ref name="SurgeonGeneralPassiveSmoking2006">{{Cite web|url=http://www.surgeongeneral.gov/library/secondhandsmoke/report/fullreport.pdf|title=The health consequences of involuntary exposure to tobacco smoke: a report of the Surgeon General|accessdate=2009-02-15|year=2006|format=PDF|publisher=U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health|location=Atlanta, U.S., page 93}}</ref> The result of scientific studies done in neonatal rats seems to indicate that exposure to cigarette smoke in the womb may reduce the fetal brain's ability to recognize [[Hypoxia (medical)|hypoxic]] conditions, thus increasing the chance of accidental [[asphyxia]]tion.<ref>{{Cite doi|10.1164/rccm.200711-1739OC}}</ref> Incidence of [[impotence]] is approximately 85 percent higher in male smokers compared to non-smokers,<ref name="tobaccoprogram.org">{{Cite web|title=The Tobacco Reference Guide|url=http://www.tobaccoprogram.org/tobaccorefguide/ch12/ch12p1.htm|accessdate=2006-07-15}}</ref> and it is a key cause of erectile dysfunction (ED).<ref name="tobaccoprogram.org"/><ref name=pmid15924009>{{Cite pmid|15924009}}</ref><ref name=pmid15146084>{{Cite doi|10.1385/ENDO:23:2-3:087}}</ref>


==Epidemiology==
==Epidemiology==
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{{Double image stack|right|Female Smoking by Country.png|Male Smoking by Country.png|250|Percentage of '''females''' smoking any tobacco product|Percentage of '''males''' smoking any tobacco product. Note that there is a difference between the scales used for females and the scales used for males.<ref>''[[#WHO2008MPOWER|WHO REPORT on the global TOBACCO epidemic]]'' 2008, pp. 267–288</ref>}}
{{Double image stack|right|Female Smoking by Country.png|Male Smoking by Country.png|250|Percentage of '''females''' smoking any tobacco product|Percentage of '''males''' smoking any tobacco product. Note that there is a difference between the scales used for females and the scales used for males.<ref>''[[#WHO2008MPOWER|WHO REPORT on the global TOBACCO epidemic]]'' 2008, pp. 267–288</ref>}}


While a more general measure of the [[Tobacco products|usage of tobacco]] (both smoked and smokeless) would be more ideal, the [[World Health Organization]] (WHO) reports "data limitations restrict the present indicator to smoked tobacco".<ref name="WHOPrevalenceAdultsAge15">{{cite web|url=http://www.who.int/whosis/indicators/compendium/2008/2ptu/en/|title=Prevalence of current tobacco use among adults aged15 years (percentage)|accessdate=2009-01-02|publisher=World Health Organization}}</ref> Smoking has therefore been studied more extensively than any other form of consumption.<ref name="WHOMayoReport">{{cite web|url=http://www.who.int/tobacco/resources/publications/mayo/en/index.html|title=Mayo report on addressing the worldwide tobacco epidemic through effective, evidence-based treatment|accessdate=2009-01-02|publisher=World Health Organization|pages=2}}</ref>
While a more general measure of the [[Tobacco products|usage of tobacco]] (both smoked and smokeless) would be more ideal, the [[World Health Organization]] (WHO) reports "data limitations restrict the present indicator to smoked tobacco".<ref name="WHOPrevalenceAdultsAge15">{{Cite web|url=http://www.who.int/whosis/indicators/compendium/2008/2ptu/en/|title=Prevalence of current tobacco use among adults aged=15 years (percentage)|accessdate=2009-01-02|publisher=World Health Organization}}</ref> Smoking has therefore been studied more extensively than any other form of consumption.<ref name="WHOMayoReport">{{Cite web|url=http://www.who.int/tobacco/resources/publications/mayo/en/index.html|title=Mayo report on addressing the worldwide tobacco epidemic through effective, evidence-based treatment|accessdate=2009-01-02|publisher=World Health Organization|pages=2}}</ref>


As of 2000, smoking is practiced by 1.22 billion people. Assuming no change in prevalence it is predicted that 1.45 billion people will smoke in 2010 and 1.5 to 1.9 billion in 2025. Assuming that prevalence will decrease at 1% a year and that there will be a modest increase of income of 2%, it is predicted the number of smokers will stand at 1.3 billion in 2010 and 2025.<ref name="HNPGuindonBoisclair13-16">{{citation|first1=G. Emmanuel|last1=Guindon|first2=David|last2=Boisclair|title=Past, current and future trends in tobacco use|url=http://www1.worldbank.org/tobacco/pdf/Guindon-Past,%20current-%20whole.pdf|format=PDF|accessdate=2009-03-22|year=2003|publisher=The International Bank for Reconstruction and Development / The World Bank|location=Washington DC|doi_brokendate=|pages=13–16}}</ref>
As of 2000, smoking is practiced by 1.22 billion people. Assuming no change in prevalence it is predicted that 1.45 billion people will smoke in 2010 and 1.5 to 1.9 billion in 2025. Assuming that prevalence will decrease at 1% a year and that there will be a modest increase of income of 2%, it is predicted the number of smokers will stand at 1.3 billion in 2010 and 2025.<ref name="HNPGuindonBoisclair13-16">{{citation|first1=G. Emmanuel|last1=Guindon|first2=David|last2=Boisclair|title=Past, current and future trends in tobacco use|url=http://www1.worldbank.org/tobacco/pdf/Guindon-Past,%20current-%20whole.pdf|format=PDF|accessdate=2009-03-22|year=2003|publisher=The International Bank for Reconstruction and Development / The World Bank|location=Washington DC|doi_brokendate=|pages=13–16}}</ref>


Smoking is generally five times more prevalent among males than females,<ref name="HNPGuindonBoisclair13-16"/> however the gender gap declines with younger age.<ref name="WomenTobaccoChallenges5-6">{{cite web|url=http://www.who.int/tobacco/media/en/WomenMonograph.pdf|format=PDF|title=Women and the Tobacco Epidemic: Challenges for the 21st Century|accessdate=2009-01-02|author=The World Health Organization, and the Institute for Global Tobacco Control, Johns Hopkins School of Public Health|year=2001|publisher=World Health Organization|pages=5–6}}</ref><ref name="2001SurgeonGeneralWomen47">{{cite web|url=http://www.cdc.gov/tobacco/data_statistics/sgr/sgr_2001/sgr_women_chapters.htm|title=Surgeon General's Report—Women and Smoking|accessdate=2009-01-03|year=2001|publisher=Centers for Disease Control and Prevention|pages=47}}</ref> In developed countries smoking rates for men have peaked and have begun to decline, however for women they continue to climb.<ref>{{citation|first1=Richard|last1=Peto|first2=Alan D|last2=Lopez|first3=Jillian|last3=Boreham|first4=Michael|last4=Thun|title=Mortality from Smoking in Developed Countries 1950-2000: indirect estimates from national vital statistics|url=http://www.ctsu.ox.ac.uk/~tobacco/SMK_All_PAGES.pdf|format=PDF|accessdate=2009-03-22|year=2006|publisher=Oxford University Press|doi_brokendate=|page=9}}</ref>
Smoking is generally five times more prevalent among males than females,<ref name="HNPGuindonBoisclair13-16"/> however the gender gap declines with younger age.<ref name="WomenTobaccoChallenges5-6">{{Cite web|url=http://www.who.int/tobacco/media/en/WomenMonograph.pdf|format=PDF|title=Women and the Tobacco Epidemic: Challenges for the 21st Century|accessdate=2009-01-02|author=The World Health Organization, and the Institute for Global Tobacco Control, Johns Hopkins School of Public Health|year=2001|publisher=World Health Organization|pages=5–6}}</ref><ref name="2001SurgeonGeneralWomen47">{{Cite web|url=http://www.cdc.gov/tobacco/data_statistics/sgr/sgr_2001/sgr_women_chapters.htm|title=Surgeon General's Report—Women and Smoking|accessdate=2009-01-03|year=2001|publisher=Centers for Disease Control and Prevention|pages=47}}</ref> In developed countries smoking rates for men have peaked and have begun to decline, however for women they continue to climb.<ref>{{citation|first1=Richard|last1=Peto|first2=Alan D|last2=Lopez|first3=Jillian|last3=Boreham|first4=Michael|last4=Thun|title=Mortality from Smoking in Developed Countries 1950-2000: indirect estimates from national vital statistics|url=http://www.ctsu.ox.ac.uk/~tobacco/SMK_All_PAGES.pdf|format=PDF|accessdate=2009-03-22|year=2006|publisher=Oxford University Press|doi_brokendate=|page=9}}</ref>


As of 2002, about twenty percent of young teens (13–15) smoke worldwide. From which 80,000 to 100,000 children begin smoking every day—roughly half of whom live in Asia. Half of those who begin smoking in [[adolescent]] years are projected to go on to smoke for 15 to 20 years.<ref name="WHO2002FactSheet">{{cite web|url=http://www.wpro.who.int/media_centre/fact_sheets/fs_20020528.htm|title=WHO/WPRO-Smoking Statistics|accessdate=2009-01-01|date=2002-05-28|publisher=World Health Organization Regional Office for the Western Pacific}}</ref>
As of 2002, about twenty percent of young teens (13–15) smoke worldwide. From which 80,000 to 100,000 children begin smoking every day—roughly half of whom live in Asia. Half of those who begin smoking in [[adolescent]] years are projected to go on to smoke for 15 to 20 years.<ref name="WHO2002FactSheet">{{Cite web|url=http://www.wpro.who.int/media_centre/fact_sheets/fs_20020528.htm|title=WHO/WPRO-Smoking Statistics|accessdate=2009-01-01|date=2002-05-28|publisher=World Health Organization Regional Office for the Western Pacific}}</ref>


The [[World Health Organization]] (WHO) states that "Much of the disease burden and premature mortality attributable to tobacco use disproportionately affect the poor". Of the 1.22 billion smokers, 1 billion of them live in developing or transitional economies. Rates of smoking have leveled off or declined in the [[developed world]].<ref>{{cite web|url=http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5644a2.htm|title=Cigarette Smoking Among Adults --- United States, 2006|accessdate=2009-01-01|author=VJ Rock, MPH, A Malarcher, PhD, JW Kahende, PhD, K Asman, MSPH, C Husten, MD, R Caraballo, PhD|date=2007-11-09|publisher=United States Centers for Disease Control and Prevention|quote=[...]In 2006, an estimated 20.8% (45.3 million) of U.S. adults[...]}}</ref> In the [[developing world]], however, tobacco consumption is rising by 3.4% per year as of 2002.<ref name="WHO2002FactSheet"/>
The [[World Health Organization]] (WHO) states that "Much of the disease burden and premature mortality attributable to tobacco use disproportionately affect the poor". Of the 1.22 billion smokers, 1 billion of them live in developing or transitional economies. Rates of smoking have leveled off or declined in the [[developed world]].<ref>{{Cite web|url=http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5644a2.htm|title=Cigarette Smoking Among Adults --- United States, 2006|accessdate=2009-01-01|author=VJ Rock, MPH, A Malarcher, PhD, JW Kahende, PhD, K Asman, MSPH, C Husten, MD, R Caraballo, PhD|date=2007-11-09|publisher=United States Centers for Disease Control and Prevention|quote=[...]In 2006, an estimated 20.8% (45.3 million) of U.S. adults[...]}}</ref> In the [[developing world]], however, tobacco consumption is rising by 3.4% per year as of 2002.<ref name="WHO2002FactSheet"/>


The WHO in 2004 projected 58.8 million deaths to occur globally,<ref name="WHO2004GBD8">''[[#WHO2004GBD|The Global Burden of Disease 2004 Update]]'' 2008, p. 8</ref> from which 5.4 million are tobacco-attributed,<ref>''[[#WHO2004GBD|The Global Burden of Disease 2004 Update]]'' 2008, p. 23</ref> and 4.9 million as of 2007.<ref name="WHO2007FactSheet">{{cite web|url=http://www.wpro.who.int/media_centre/fact_sheets/fs_20070529.htm|title=WHO/WPRO-Tobacco Fact sheet|accessdate=2009-01-01|date=2007-05-29|publisher=World Health Organization Regional Office for the Western Pacific}}</ref> As of 2002, 70% of the deaths are in developing countries.<ref name="WHO2007FactSheet"/>
The WHO in 2004 projected 58.8 million deaths to occur globally,<ref name="WHO2004GBD8">''[[#WHO2004GBD|The Global Burden of Disease 2004 Update]]'' 2008, p. 8</ref> from which 5.4 million are tobacco-attributed,<ref>''[[#WHO2004GBD|The Global Burden of Disease 2004 Update]]'' 2008, p. 23</ref> and 4.9 million as of 2007.<ref name="WHO2007FactSheet">{{Cite web|url=http://www.wpro.who.int/media_centre/fact_sheets/fs_20070529.htm|title=WHO/WPRO-Tobacco Fact sheet|accessdate=2009-01-01|date=2007-05-29|publisher=World Health Organization Regional Office for the Western Pacific}}</ref> As of 2002, 70% of the deaths are in developing countries.<ref name="WHO2007FactSheet"/>


The shift in prevalence of tobacco smoking to a younger demographic, mainly in the developing world, can be attributed to several factors. The tobacco industry spends up to $12.5 billion dollars annually on advertising, which is increasingly geared towards adolescents in the third world because they are a very vulnerable audience for the marketing campaigns. Adolescents have more difficulty understanding the long term health risks that are associated with smoking and are also more easily influence by “images of romance, success, sophistication, popularity, and adventure which advertising suggests they could achieve through the consumption of cigarettes”. This shift in marketing towards adolescents and even children in the tobacco industry is debilitating to organizations’ and countries’ efforts to improve child health and mortality in the developing world. It reverses or halts the effects of the work that has been done to improve health care in these countries, and although smoking is deemed as a “voluntary” health risk, the marketing of tobacco towards very impressionable adolescents in the developing world makes it less of a voluntary action and more of an inevitable shift.<ref> Nichter, M., and E. Cartwright. 1991. Saving the children for the tobacco industry. Medical
The shift in prevalence of tobacco smoking to a younger demographic, mainly in the developing world, can be attributed to several factors. The tobacco industry spends up to $12.5 billion dollars annually on advertising, which is increasingly geared towards adolescents in the third world because they are a very vulnerable audience for the marketing campaigns. Adolescents have more difficulty understanding the long term health risks that are associated with smoking and are also more easily influence by “images of romance, success, sophistication, popularity, and adventure which advertising suggests they could achieve through the consumption of cigarettes”. This shift in marketing towards adolescents and even children in the tobacco industry is debilitating to organizations’ and countries’ efforts to improve child health and mortality in the developing world. It reverses or halts the effects of the work that has been done to improve health care in these countries, and although smoking is deemed as a “voluntary” health risk, the marketing of tobacco towards very impressionable adolescents in the developing world makes it less of a voluntary action and more of an inevitable shift.<ref>Nichter, M., and E. Cartwright. 1991. Saving the children for the tobacco industry. Medical
Anthropology Quarterly 5 (3):236-256.</ref>
Anthropology Quarterly 5 (3):236-256.</ref>


===Studies===
===Studies===
In 1938 a study by a [[John Hopkins University]] scientist suggested a strongly negative correlation between smoking and lifespan. In 1950 five studies were published in which "smoking was powerfully implicated in the causation of lung cancer".<ref name=dm/> These included the now classic paper "Smoking and Carcinoma of the Lung" which appeared in the ''[[British Medical Journal]]''. This paper reported that "heavy smokers were fifty times as likely as non-smokers to contract lung cancer".<ref name=dm>[[David Michaels (epidemiologist)|David Michaels]] (2008). ''Doubt is Their Product'', Oxford University Press, pp. 4-5.</ref><ref>{{cite journal |author=Doll R, Hill AB |title=Smoking and carcinoma of the lung; preliminary report |journal=Br Med J |volume=2 |issue=4682 |pages=739–48 |year=1950 |month=September |pmid=14772469 |pmc=2038856 |doi= |url=}}</ref>
In 1938 a study by a [[John Hopkins University]] scientist suggested a strongly negative correlation between smoking and lifespan. In 1950 five studies were published in which "smoking was powerfully implicated in the causation of lung cancer".<ref name=dm/> These included the now classic paper "Smoking and Carcinoma of the Lung" which appeared in the ''[[British Medical Journal]]''. This paper reported that "heavy smokers were fifty times as likely as non-smokers to contract lung cancer".<ref name=dm>[[David Michaels (epidemiologist)|David Michaels]] (2008). ''Doubt is Their Product'', Oxford University Press, pp. 4-5.</ref><ref>{{Cite pmid|14772469}}</ref>


A team of British scientists headed by [[Richard Doll]] carried out a longitudinal study of 34,439 medical specialists from 1951 to 2001, generally called the "[[British doctors study]]."<ref name="bmj.bmjjournals.com.331">{{cite journal|author=Richard Doll, Richard Peto, Jillian Boreham, Isabelle Sutherland|year=2004|month=June|title=Mortality in relation to smoking: 50 years' observations on male British doctors|journal=BMJ|volume=328|issue=1519|page=1519|url=http://bmj.bmjjournals.com/cgi/content/abstract/328/7455/1519|pmid=15213107|doi=10.1136/bmj.38142.554479.AE }}</ref> The study demonstrated that that about half of the
A team of British scientists headed by [[Richard Doll]] carried out a longitudinal study of 34,439 medical specialists from 1951 to 2001, generally called the "[[British doctors study]]."<ref name="bmj.bmjjournals.com.331">{{Cite doi|10.1136/bmj.38142.554479.AE}}</ref> The study demonstrated that that about half of the persistent cigarette smokers born in 1900-1909 were eventually killed by their habit (calculated from the [[logarithm]]s of the probabilities of surviving from 35-70, 70-80, and 80-90) and about two thirds of the persistent cigarette smokers born in the 1920s would eventually be killed by their habit. After a ban on smoking in all enclosed public places was introduced in Scotland in March 2006, there was a 17 percent reduction in hospital admissions for acute coronary syndrome. 67% of the decrease occurred in non-smokers.<ref>{{Cite doi|10.1056/NEJMsa0706740}}</ref>
persistent cigarette smokers born in 1900-1909 were eventually
killed by their habit (calculated from the [[logarithm]]s of the probabilities of surviving
from 35-70, 70-80, and 80-90) and about two thirds of the persistent cigarette smokers
born in the 1920s would eventually be killed by their habit.
After a ban on smoking in all enclosed public places was introduced in Scotland in March 2006, there was a 17 percent reduction in hospital admissions for acute coronary syndrome. 67% of the decrease occurred in non-smokers.<ref>{{cite journal|author=Pell JP, Haw S, Cobbe S, ''et al.''|title=Smoke-free legislation and hospitalizations for acute coronary syndrome|journal=N. Engl. J. Med.|volume=359|issue=5|pages=482–91|year=2008|month=July|pmid=18669427|doi=10.1056/NEJMsa0706740|url=}}</ref>


The health effects of tobacco have been significant for the development of the science of [[epidemiology]]. As the mechanism of carcinogenicity is radiomimetic or radiological, the effects are [[stochastic]]. Definite statements can be made only on the relative increased or decreased probabilities of contracting a given disease; Philosophically and theoretically speaking, it is impossible to definitively prove a direct causative link between exposure to a radiomimetic poison such as tobacco smoke and the cancer that follows. Tobacco companies have capitalized on this philosophical objection and exploited the doubts of clinicians, who consider only individual cases, on the causal link in the stochastic expression of the toxicity as actual disease.<ref name="Hesari">Review (Helsingin Sanomat 30.3.2008, [http://www.hs.fi/juttusarja/maailmankirjat/artikkeli/Savukkeet+loivat+Amerikan/1135235163312]) on Allan M. Brandt: The Cigarette Century. Basic Books. ISBN 978-0465070473. http://www.cigarettecentury.com/</ref>
The health effects of tobacco have been significant for the development of the science of [[epidemiology]]. As the mechanism of carcinogenicity is radiomimetic or radiological, the effects are [[stochastic]]. Definite statements can be made only on the relative increased or decreased probabilities of contracting a given disease; Philosophically and theoretically speaking, it is impossible to definitively prove a direct causative link between exposure to a radiomimetic poison such as tobacco smoke and the cancer that follows. Tobacco companies have capitalized on this philosophical objection and exploited the doubts of clinicians, who consider only individual cases, on the causal link in the stochastic expression of the toxicity as actual disease.<ref name="Hesari">Review (Helsingin Sanomat 30.3.2008, [http://www.hs.fi/juttusarja/maailmankirjat/artikkeli/Savukkeet+loivat+Amerikan/1135235163312]) on Allan M. Brandt: The Cigarette Century. Basic Books. ISBN 978-0465070473. http://www.cigarettecentury.com/</ref>
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There have been multiple court cases on the issue that tobacco companies have researched the health effects of tobacco, but suppressed the findings or formatted them to imply lessened or no hazard.<ref name="Hesari" />
There have been multiple court cases on the issue that tobacco companies have researched the health effects of tobacco, but suppressed the findings or formatted them to imply lessened or no hazard.<ref name="Hesari" />


A study published in the journal Pediatrics<ref>{{cite journal |author=Winickoff JP, Friebely J, Tanski SE, ''et al.'' |title=Beliefs about the health effects of "thirdhand" smoke and home smoking bans |journal=Pediatrics |volume=123 |issue=1 |pages=e74–9 |year=2009 |month=January |pmid=19117850 |doi=10.1542/peds.2008-2184}}</ref> refers to the danger posed by what the authors call "third-hand smoke" — toxic substances that remain in areas where smoking has recently occurred. The study was [http://www.voanews.com/english/Science/2009-01-09-voa71.cfm reviewed in an story] broadcast by the [[Voice of America]].
A study published in the journal Pediatrics<ref>{{Cite doi|10.1542/peds.2008-2184}}</ref> refers to the danger posed by what the authors call "third-hand smoke" — toxic substances that remain in areas where smoking has recently occurred. The study was [http://www.voanews.com/english/Science/2009-01-09-voa71.cfm reviewed in an story] broadcast by the [[Voice of America]].


===Occasional Smoking===
===Occasional Smoking===
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{{Double image stack|right|Benzopyrene diol epoxide chemical structure.png|Benzopyrene DNA adduct 1JDG.png|200|Benzopyrene diol epoxide, an extremely carcinogenic (cancer-causing) metabolite of benzopyrene, a polynuclear aromatic hydrocarbon produced by burning tobacco.|Benzopyrene, a major mutagen in tobacco smoke, in an [[adduct]] to DNA.<ref>Created from [http://www.rcsb.org/pdb/cgi/explore.cgi?pdbId=1JDG PDB 1JDG]</ref>}}
{{Double image stack|right|Benzopyrene diol epoxide chemical structure.png|Benzopyrene DNA adduct 1JDG.png|200|Benzopyrene diol epoxide, an extremely carcinogenic (cancer-causing) metabolite of benzopyrene, a polynuclear aromatic hydrocarbon produced by burning tobacco.|Benzopyrene, a major mutagen in tobacco smoke, in an [[adduct]] to DNA.<ref>Created from [http://www.rcsb.org/pdb/cgi/explore.cgi?pdbId=1JDG PDB 1JDG]</ref>}}


Smoke, or any partially burnt organic matter, is [[carcinogen]]ic (cancer-causing). The damage a continuing smoker does to their lungs can take up to 20 years before its physical manifestation in lung cancer. Women began smoking later than men, so the rise in death rate amongst women did not appear until later. The male lung cancer death rate decreased in 1975 &mdash; roughly 20 years after the fall in cigarette consumption in men. A fall in consumption in women also began in 1975 but by 1991 had not manifested in a decrease in lung cancer related mortalities amongst women.<ref>{{cite book|author=Jones Mary, Fosbery Richard, Taylor Dennis|title=Biology 1|chapter=Answers to self-assessment questions|page=250|publisher=Cambridge Advanced Sciences|isbn=0-521-78719-X|year=2000}}</ref>
Smoke, or any partially burnt organic matter, is [[carcinogen]]ic (cancer-causing). The damage a continuing smoker does to their lungs can take up to 20 years before its physical manifestation in lung cancer. Women began smoking later than men, so the rise in death rate amongst women did not appear until later. The male lung cancer death rate decreased in 1975 &mdash; roughly 20 years after the fall in cigarette consumption in men. A fall in consumption in women also began in 1975 but by 1991 had not manifested in a decrease in lung cancer related mortalities amongst women.<ref>{{Cite book|author=Jones Mary, Fosbery Richard, Taylor Dennis|title=Biology 1|chapter=Answers to self-assessment questions|page=250|publisher=Cambridge Advanced Sciences|isbn=0-521-78719-X|year=2000}}</ref>


Smoke contains several carcinogenic [[pyrolysis|pyrolytic]] products that bind to [[DNA]] and cause [[genetic mutation]]s. Particularly potent carcinogens are [[polynuclear aromatic hydrocarbons]] (PAH), which are [[Toxication|toxicated]] to [[mutagenic]] [[epoxide]]s. The first PAH to be identified as a carcinogen in tobacco smoke was [[benzopyrene]], which has been shown to toxicate into an epoxide that irreversibly attaches to a cell's nuclear DNA, which may either kill the cell or cause a [[genetic mutation]]. If the mutation inhibits [[programmed cell death]], the cell can survive to become a [[cancer cell]]. Similarly, [[acrolein]], which is abundant in tobacco smoke, also irreversibly binds to DNA, causes mutations and thus also cancer. However, it needs no activation to become carcinogenic.<ref name="Feng">{{cite journal|last=Feng|first=Z|coauthors=Hu W, Hu Y, Tang M|title=Acrolein is a major cigarette-related lung cancer agent: Preferential binding at p53 mutational hotspots and inhibition of DNA repair|journal=[[Proceedings of the National Academy of Sciences]]|volume=103|issue=42|pages=15404–15409|month=October|year=2006|url=http://www.pnas.org/cgi/reprint/0607031103v1|pmid=17030796|doi=10.1073/pnas.0607031103}}</ref>
Smoke contains several carcinogenic [[pyrolysis|pyrolytic]] products that bind to [[DNA]] and cause [[genetic mutation]]s. Particularly potent carcinogens are [[polynuclear aromatic hydrocarbons]] (PAH), which are [[Toxication|toxicated]] to [[mutagenic]] [[epoxide]]s. The first PAH to be identified as a carcinogen in tobacco smoke was [[benzopyrene]], which has been shown to toxicate into an epoxide that irreversibly attaches to a cell's nuclear DNA, which may either kill the cell or cause a [[genetic mutation]]. If the mutation inhibits [[programmed cell death]], the cell can survive to become a [[cancer cell]]. Similarly, [[acrolein]], which is abundant in tobacco smoke, also irreversibly binds to DNA, causes mutations and thus also cancer. However, it needs no activation to become carcinogenic.<ref name="Feng">{{Cite doi|10.1073/pnas.0607031103}}</ref>


There are over 19 known [[carcinogens]] in cigarette smoke.<ref>{{cite web|author=Dr. [[C. Everett Koop]]|title=Smoking and smokeless tobacco|url=http://www.drkoop.com/ency/93/002032.html|accessdate=July 15, 2006}}</ref> The following are some of the most potent carcinogens:
There are over 19 known [[carcinogens]] in cigarette smoke.<ref>{{Cite web|author=Dr. [[C. Everett Koop]]|title=Smoking and smokeless tobacco|url=http://www.drkoop.com/ency/93/002032.html|accessdate=July 15, 2006}}</ref> The following are some of the most potent carcinogens:
* '''[[Polycyclic aromatic hydrocarbon|Polynuclear aromatic hydrocarbons]]''' are [[Tar (tobacco residue)|tar]] components produced by [[pyrolysis]] in smoldering organic matter and emitted into smoke. Many of them are highly carcinogenic and mutagenic, because they are [[Toxication|toxicated]] to [[mutagenic]] [[epoxide]]s, which are [[electrophilic alkylating agent]]s. The first PAH to be identified as a carcinogen in tobacco smoke was '''[[benzopyrene]]''', which been shown to toxicate into a diol epoxide and then permanently attach to nuclear DNA, which may either kill the cell or cause a [[genetic mutation]]. The DNA contains the information on how the cell function; in practice, it contains the recipes for protein synthesis. If the mutation inhibits [[programmed cell death]], the cell can survive to become a [[cancer cell]], a cell that does not function like a normal cell. The carcinogenity is radiomimetic, i.e. similar to that produced by ionizing nuclear radiation. Tobacco manufacturers have experimented with combustionless [[vaporizer]] technology to allow cigarettes to be consumed without the formation of carcinogenic benzopyrenes.<ref>{{cite web|title=DNA interaction with Benzopyrene|work=DNA|url=http://www.mybiology.com/chime/dna_benzopyrene/dna_benzopyrene_text.htm|accessdate=March 5, 2005}}</ref> However, such products have not become popular.
* '''[[Polycyclic aromatic hydrocarbon|Polynuclear aromatic hydrocarbons]]''' are [[Tar (tobacco residue)|tar]] components produced by [[pyrolysis]] in smoldering organic matter and emitted into smoke. Many of them are highly carcinogenic and mutagenic, because they are [[Toxication|toxicated]] to [[mutagenic]] [[epoxide]]s, which are [[electrophilic alkylating agent]]s. The first PAH to be identified as a carcinogen in tobacco smoke was '''[[benzopyrene]]''', which been shown to toxicate into a diol epoxide and then permanently attach to nuclear DNA, which may either kill the cell or cause a [[genetic mutation]]. The DNA contains the information on how the cell function; in practice, it contains the recipes for protein synthesis. If the mutation inhibits [[programmed cell death]], the cell can survive to become a [[cancer cell]], a cell that does not function like a normal cell. The carcinogenity is radiomimetic, i.e. similar to that produced by ionizing nuclear radiation. Tobacco manufacturers have experimented with combustionless [[vaporizer]] technology to allow cigarettes to be consumed without the formation of carcinogenic benzopyrenes.<ref>{{Cite web|title=DNA interaction with Benzopyrene|work=DNA|url=http://www.mybiology.com/chime/dna_benzopyrene/dna_benzopyrene_text.htm|accessdate=March 5, 2005}}</ref> However, such products have not become popular.
* '''[[Acrolein]]''' is a pyrolysis product that is abundant in cigarette smoke. It gives smoke an acrid smell and an irritating, lachromatory effect and is a major contributor to its carcinogenity. Like PAH metabolites, acrolein is also an electrophilic alkylating agent and permanently binds to the DNA base [[guanine]], by a [[conjugate addition]] followed by cyclization into a [[hemiaminal]]. The acrolein-guanine adduct induces mutations during DNA copying and thus causes cancers in a manner similar to PAHs. However, acrolein is 1000 times more abundant than PAHs in cigarette smoke, and is able to react as is, without metabolic activation. Acrolein has been shown to be a [[mutagen]] and [[carcinogen]] in human cells. The carcinogenity of acrolein has been difficult to study by [[animal experimentation]], because it has such a toxicity that it tends to kill the animals before they develop cancer.<ref name="Feng">{{cite journal|last=Feng|first=Z|coauthors=Hu W, Hu Y, Tang M|title=Acrolein is a major cigarette-related lung cancer agent: Preferential binding at p53 mutational hotspots and inhibition of DNA repair|journal=[[Proceedings of the National Academy of Sciences]]|volume=103|issue=42|pages=15404–9|month=October|year=2006|url=http://www.pnas.org/cgi/reprint/0607031103v1|pmid=17030796|doi=10.1073/pnas.0607031103}}</ref> Generally, compounds able to react by [[conjugate addition]] as [[electrophile]]s (so-called ''Michael acceptors'' after [[Michael reaction]]) are toxic and carcinogenic, because they can permanently alkylate DNA, similarly to [[mustard gas]] or [[aflatoxin]]. Acrolein is only one of them present in cigarette smoke; for example, [[crotonaldehyde]] has been found in cigarette smoke.<ref name="Kataoka">Kataoka, H. et al. Chromatographia, Volume 44, Numbers 9-10 / May, Pages 491-496, 1997. DOI: 10.1007/BF02466742</ref> Michael acceptors also contribute to the chronic inflammation present in tobacco disease.<ref name="Facchinetti" />
* '''[[Acrolein]]''' is a pyrolysis product that is abundant in cigarette smoke. It gives smoke an acrid smell and an irritating, lachromatory effect and is a major contributor to its carcinogenity. Like PAH metabolites, acrolein is also an electrophilic alkylating agent and permanently binds to the DNA base [[guanine]], by a [[conjugate addition]] followed by cyclization into a [[hemiaminal]]. The acrolein-guanine adduct induces mutations during DNA copying and thus causes cancers in a manner similar to PAHs. However, acrolein is 1000 times more abundant than PAHs in cigarette smoke, and is able to react as is, without metabolic activation. Acrolein has been shown to be a [[mutagen]] and [[carcinogen]] in human cells. The carcinogenity of acrolein has been difficult to study by [[animal experimentation]], because it has such a toxicity that it tends to kill the animals before they develop cancer.<ref name="Feng">{{Cite doi|10.1073/pnas.0607031103}}</ref> Generally, compounds able to react by [[conjugate addition]] as [[electrophile]]s (so-called ''Michael acceptors'' after [[Michael reaction]]) are toxic and carcinogenic, because they can permanently alkylate DNA, similarly to [[mustard gas]] or [[aflatoxin]]. Acrolein is only one of them present in cigarette smoke; for example, [[crotonaldehyde]] has been found in cigarette smoke.<ref name="Kataoka">Kataoka, H. et al. Chromatographia, Volume 44, Numbers 9-10 / May, Pages 491-496, 1997. DOI: 10.1007/BF02466742</ref> Michael acceptors also contribute to the chronic inflammation present in tobacco disease.<ref name="Facchinetti" />
* '''[[Nitrosamine]]s''' are a group of carcinogenic compounds found in cigarette smoke but not in uncured tobacco leaves. Nitrosamines form on flue-cured tobacco leaves during the curing process through a [[chemical reaction]] between nicotine and other compounds contained in the uncured leaf and various oxides of nitrogen found in all combustion gases. Switching to [[Indirect fire|indirect-fire]] curing has been shown to reduce nitrosamine levels to less than 0.1 parts per million.<ref>{{cite web|author=Sumner et al.|title=Retrofitting Tobacco Curing Barns|url=http://www.tifton.uga.edu/tobacco/retrofitinfo.htm|accessdate=June 9, 2006}}</ref><ref>{{cite web|author=[[NOVA]]|url=http://www.pbs.org/wgbh/nova/cigarette/history2.html|title=Search for a Safer Cigarette}}</ref>
* '''[[Nitrosamine]]s''' are a group of carcinogenic compounds found in cigarette smoke but not in uncured tobacco leaves. Nitrosamines form on flue-cured tobacco leaves during the curing process through a [[chemical reaction]] between nicotine and other compounds contained in the uncured leaf and various oxides of nitrogen found in all combustion gases. Switching to [[Indirect fire|indirect-fire]] curing has been shown to reduce nitrosamine levels to less than 0.1 parts per million.<ref>{{Cite web|author=Sumner et al.|title=Retrofitting Tobacco Curing Barns|url=http://www.tifton.uga.edu/tobacco/retrofitinfo.htm|accessdate=June 9, 2006}}</ref><ref>{{Cite web|author=[[NOVA]]|url=http://www.pbs.org/wgbh/nova/cigarette/history2.html|title=Search for a Safer Cigarette}}</ref>


===Radioactive carcinogens===
===Radioactive carcinogens===
In addition to chemical, nonradioactive carcinogens, tobacco and tobacco smoke contain small amounts of [[lead-210]] (<sup>210</sup>Pb) and [[polonium-210]] (<sup>210</sup>Po) both of which are radioactive carcinogens. The presence of polonium-210 in mainstream cigarette smoke has been experimentally measured at levels of 0.0263&ndash;0.036 pCi (0.97–1.33 mBq),<ref>{{cite web|url=http://chppm-www.apgea.army.mil/documents/TG/TECHGUID/TG238.pdf|author=[[U.S. Army]] Center for Health Promotion and Preventive Medicine|title=Radiological Sources of Potential Exposure and/or Contamination|format=PDF}}</ref> which is equivalent to about 0.1 pCi per milligram of smoke (4 mBq/mg); or about 0.81 pCi of lead 210 per gram of dry condensed smoke (30 Bq/kg).
In addition to chemical, nonradioactive carcinogens, tobacco and tobacco smoke contain small amounts of [[lead-210]] (<sup>210</sup>Pb) and [[polonium-210]] (<sup>210</sup>Po) both of which are radioactive carcinogens. The presence of polonium-210 in mainstream cigarette smoke has been experimentally measured at levels of 0.0263&ndash;0.036 pCi (0.97–1.33 mBq),<ref>{{Cite web|url=http://chppm-www.apgea.army.mil/documents/TG/TECHGUID/TG238.pdf|author=[[U.S. Army]] Center for Health Promotion and Preventive Medicine|title=Radiological Sources of Potential Exposure and/or Contamination|format=PDF}}</ref> which is equivalent to about 0.1 pCi per milligram of smoke (4 mBq/mg); or about 0.81 pCi of lead 210 per gram of dry condensed smoke (30 Bq/kg).


Research by [[NCAR]] [[radiochemistry|radiochemist]] [[Ed Martell]] determined that radioactive compounds in cigarette smoke are deposited in "hot spots" where [[bronchial tubes]] branch. Since tar from cigarette smoke is resistant to dissolving in lung fluid, the radioactive compounds have a great deal of time to undergo [[radioactive decay]] before being cleared by natural processes. Indoors, these radioactive compounds linger in secondhand smoke, and therefore greater exposure occurs when these radioactive compounds are inhaled during normal breathing, which is deeper and longer than when inhaling cigarettes. Damage to the protective [[epithelial]] tissue from smoking only increases the prolonged retention of insoluble polonium 210 compounds produced from burning tobacco. Martell estimated that a carcinogenic radiation dose of 80-100 rads is delivered the lung tissue of most smokers who die of lung cancer.<ref>{{cite web|author=[[Edward Martell|E. A. Martell]]|year=[[1983]]|title=Radiation Dose at Bronchial Bifurcations of Smokers from Indoor Exposure to Radon Progeny|url=http://www.pnas.org/cgi/content/abstract/80/5/1285|accessdate=June 9, 2006}}</ref>
Research by [[NCAR]] [[radiochemistry|radiochemist]] [[Ed Martell]] determined that radioactive compounds in cigarette smoke are deposited in "hot spots" where [[bronchial tubes]] branch. Since tar from cigarette smoke is resistant to dissolving in lung fluid, the radioactive compounds have a great deal of time to undergo [[radioactive decay]] before being cleared by natural processes. Indoors, these radioactive compounds linger in secondhand smoke, and therefore greater exposure occurs when these radioactive compounds are inhaled during normal breathing, which is deeper and longer than when inhaling cigarettes. Damage to the protective [[epithelial]] tissue from smoking only increases the prolonged retention of insoluble polonium 210 compounds produced from burning tobacco. Martell estimated that a carcinogenic radiation dose of 80-100 rads is delivered the lung tissue of most smokers who die of lung cancer.<ref>{{Cite web|author=[[Edward Martell|E. A. Martell]]|year=[[1983]]|title=Radiation Dose at Bronchial Bifurcations of Smokers from Indoor Exposure to Radon Progeny|url=http://www.pnas.org/cgi/content/abstract/80/5/1285|accessdate=June 9, 2006}}</ref>


The view that polonium 210 is responsible for many cases of cancer in tobacco smokers is disputed by at least one researcher.<ref name="hecht1997">{{cite journal|last=Hecht|first=Stephen S.|title=Approaches to Chemoprevention of Lung Cancer Based on Carcinogens in Tobacco Smoke|month=June|year=1997|journal=Environmental Health Perspectives|volume=105|issue=S4|url=http://www.ehponline.org/members/1997/Suppl-4/hecht-full.html|accessdate=2006-12-06 }}</ref><ref name="hecht1999"> {{cite journal|last=Hecht|first=Stephen S.|title=Tobacco Smoke Carcinogens and Lung Cancer|date=July 21, 1999|journal=Journal of the National Cancer Institute|volume=91|issue=14|pages=1194–1210|url=http://jncicancerspectrum.oxfordjournals.org/cgi/content/full/jnci;91/14/1194|accessdate=2006-12-06|doi=10.1093/jnci/91.14.1194|pmid=10413421 }}</ref>
The view that polonium 210 is responsible for many cases of cancer in tobacco smokers is disputed by at least one researcher.<ref name="hecht1997">{{Cite journal|last=Hecht|first=Stephen S.|title=Approaches to Chemoprevention of Lung Cancer Based on Carcinogens in Tobacco Smoke|month=June|year=1997|journal=Environmental Health Perspectives|volume=105|issue=S4|url=http://www.ehponline.org/members/1997/Suppl-4/hecht-full.html|accessdate=2006-12-06 }}</ref><ref name="hecht1999">{{Cite pmid|10413421 }}</ref>


===Nicotine===
===Nicotine===


[[Image:Nicotine-2D-skeletal.png|thumb|right|Nicotine molecule]]
[[File:Nicotine-2D-skeletal.png|thumb|Nicotine molecule]]


[[Nicotine]] that is contained in cigarettes and other smoked tobacco products is a [[stimulant]] and is one of the main factors leading to continued tobacco smoking. Although the amount of nicotine inhaled with tobacco smoke is quite small (most of the substance is destroyed by the heat) it is still sufficient to cause physical and/or psychological [[Chemical dependency|dependence]]. The amount of nicotine absorbed by the body from smoking depends on many factors, including the type of tobacco, whether the smoke is inhaled, and whether a filter is used. Despite the design of various cigarettes advertised and even tested on machines to deliver less of the toxic tar, studies show that when smoked by humans instead of machines, they deliver the same net amount of smoke. Ingesting a compound by smoking is one of the most rapid and efficient methods of introducing it into the bloodstream, second only to injection, which allows for the rapid feedback which supports the smokers' ability to [[Titration|titrate]] their dosage. On average it takes about ten seconds for the substance to reach the brain. As a result of the efficiency of this delivery system, many smokers feel as though they are unable to cease. Of those who attempt cessation and last three months without succumbing to nicotine, most are able to remain smoke free for the rest of their lives.<ref name=NCI_quit>[http://www.cancer.gov/cancertopics/factsheet/Tobacco/cessation Quitting Smoking: Why To Quit and How To Get Help - National Cancer Institute<!-- Bot generated title -->]</ref> There exists a possibility of depression in some who attempt cessation, as with other psychoactive substances. Depression is also common in teenage smokers; teens who smoke are four times as likely to develop depressive symptoms as their nonsmoking peers.<ref>[http://www.apa.org/monitor/dec00/smoking.html Smoking increases teen depression<!-- Bot generated title -->]</ref>
[[Nicotine]] that is contained in cigarettes and other smoked tobacco products is a [[stimulant]] and is one of the main factors leading to continued tobacco smoking. Although the amount of nicotine inhaled with tobacco smoke is quite small (most of the substance is destroyed by the heat) it is still sufficient to cause physical and/or psychological [[Chemical dependency|dependence]]. The amount of nicotine absorbed by the body from smoking depends on many factors, including the type of tobacco, whether the smoke is inhaled, and whether a filter is used. Despite the design of various cigarettes advertised and even tested on machines to deliver less of the toxic tar, studies show that when smoked by humans instead of machines, they deliver the same net amount of smoke. Ingesting a compound by smoking is one of the most rapid and efficient methods of introducing it into the bloodstream, second only to injection, which allows for the rapid feedback which supports the smokers' ability to [[Titration|titrate]] their dosage. On average it takes about ten seconds for the substance to reach the brain. As a result of the efficiency of this delivery system, many smokers feel as though they are unable to cease. Of those who attempt cessation and last three months without succumbing to nicotine, most are able to remain smoke free for the rest of their lives.<ref name=NCI_quit>[http://www.cancer.gov/cancertopics/factsheet/Tobacco/cessation Quitting Smoking: Why To Quit and How To Get Help - National Cancer Institute<!-- Bot generated title -->]</ref> There exists a possibility of depression in some who attempt cessation, as with other psychoactive substances. Depression is also common in teenage smokers; teens who smoke are four times as likely to develop depressive symptoms as their nonsmoking peers.<ref>[http://www.apa.org/monitor/dec00/smoking.html Smoking increases teen depression<!-- Bot generated title -->]</ref>


Although nicotine does play a role in acute episodes of some diseases (including [[stroke]], [[impotence]], and [[heart disease]]) by its stimulation of [[adrenaline]] release, which raises [[blood pressure]],<ref>{{cite journal|author=Narkiewicz K, Kjeldsen SE, Hedner T|title=Is smoking a causative factor of hypertension?|journal=Blood Press.|volume=14|issue=2|pages=69–71|year=2005|pmid=16036482|doi=10.1080/08037050510034202}}</ref> [[heart rate]], and [[free fatty acids]], the most serious longer term effects are more the result of the products of the smouldering combustion process. This has enabled development of various nicotine delivery systems, such as the [[nicotine patch]] or [[nicotine gum]], that can satisfy the addictive craving by delivering nicotine without the harmful combustion by-products. This can help the heavily dependent smoker to quit gradually, while discontinuing further damage to health.
Although nicotine does play a role in acute episodes of some diseases (including [[stroke]], [[impotence]], and [[heart disease]]) by its stimulation of [[adrenaline]] release, which raises [[blood pressure]],<ref>{{Cite doi|10.1080/08037050510034202}}</ref> [[heart rate]], and [[free fatty acids]], the most serious longer term effects are more the result of the products of the smouldering combustion process. This has enabled development of various nicotine delivery systems, such as the [[nicotine patch]] or [[nicotine gum]], that can satisfy the addictive craving by delivering nicotine without the harmful combustion by-products. This can help the heavily dependent smoker to quit gradually, while discontinuing further damage to health.


[[Nicotine]] is a highly addictive psychoactive chemical. When tobacco is smoked, most of the nicotine is [[Pyrolysis|pyrolyzed]]; a dose sufficient to cause mild somatic dependency and mild to strong psychological dependency remains. There is also a formation of [[Harmala|harmane]] (a [[MAO inhibitor]]) from the acetaldehyde in cigarette smoke, which seems to play an important role in nicotine addiction<ref>{{cite journal|author=Talhout R, Opperhuizen A, van Amsterdam JG|title=Role of acetaldehyde in tobacco smoke addiction|journal=Eur Neuropsychopharmacol|volume=17|issue=10|pages=627–36|year=2007|month=October|pmid=17382522|doi=10.1016/j.euroneuro.2007.02.013 }}</ref> probably by facilitating dopamine release in the nucleus accumbens in response to nicotine stimuli. According to studies by Henningfield and Benowitz, nicotine is more addictive than [[Cannabis (drug)|cannabis]], [[caffeine]], [[ethanol]], [[cocaine]], and [[heroin]] when considering both somatic and psychological dependence. However, due to the stronger withdrawal effects of [[ethanol]], [[cocaine]] and [[heroin]], nicotine may have a lower potential for somatic dependence than these substances.<ref>[http://www.tfy.drugsense.org/tfy/addictvn.htm Relative Addictiveness of Drugs]</ref><ref>[http://b.rox.com/gizmos/henningfield-benowitz/combo.swf The Henningfield-Benowitz substance comparison charts]</ref> A study by Perrine concludes that nicotine's potential for psychological dependency exceeds all other studied drugs{{Citation needed|date=October 2009}} - even ethanol, an extremely physically addictive substance with severe [[Delirium tremens|withdrawal]] symptoms that can be fatal. About half of Canadians who currently smoke have tried to quit.<ref> [http://tobacco.aadac.com/about_tobacco/addiction/ AADAC|Truth About Tobacco - Addiction]</ref> [[McGill University]] health professor Jennifer O'Loughlin stated that nicotine addiction can occur as soon as five months after the start of smoking.<ref> [http://lfpress.ca/newsstand/Today/2006/08/02/1714754-sun.html Cigarette addiction faster than expected.] ''The London Free Press'' (August 2, 2006).</ref>
[[Nicotine]] is a highly addictive psychoactive chemical. When tobacco is smoked, most of the nicotine is [[Pyrolysis|pyrolyzed]]; a dose sufficient to cause mild somatic dependency and mild to strong psychological dependency remains. There is also a formation of [[Harmala|harmane]] (a [[MAO inhibitor]]) from the acetaldehyde in cigarette smoke, which seems to play an important role in nicotine addiction<ref>{{Cite doi|10.1016/j.euroneuro.2007.02.013}}</ref> probably by facilitating dopamine release in the nucleus accumbens in response to nicotine stimuli. According to studies by Henningfield and Benowitz, nicotine is more addictive than [[Cannabis (drug)|cannabis]], [[caffeine]], [[ethanol]], [[cocaine]], and [[heroin]] when considering both somatic and psychological dependence. However, due to the stronger withdrawal effects of [[ethanol]], [[cocaine]] and [[heroin]], nicotine may have a lower potential for somatic dependence than these substances.<ref>[http://www.tfy.drugsense.org/tfy/addictvn.htm Relative Addictiveness of Drugs]</ref><ref>[http://b.rox.com/gizmos/henningfield-benowitz/combo.swf The Henningfield-Benowitz substance comparison charts]</ref> A study by Perrine concludes that nicotine's potential for psychological dependency exceeds all other studied drugs{{Citation needed|date=October 2009}} - even ethanol, an extremely physically addictive substance with severe [[Delirium tremens|withdrawal]] symptoms that can be fatal. About half of Canadians who currently smoke have tried to quit.<ref>[http://tobacco.aadac.com/about_tobacco/addiction/ AADAC|Truth About Tobacco - Addiction]</ref> [[McGill University]] health professor Jennifer O'Loughlin stated that nicotine addiction can occur as soon as five months after the start of smoking.<ref>[http://lfpress.ca/newsstand/Today/2006/08/02/1714754-sun.html Cigarette addiction faster than expected.] ''The London Free Press'' (August 2, 2006).</ref>


Recent evidence has shown that smoking tobacco increases the release of [[dopamine]] in the brain, specifically in the mesolimbic pathway, the same neuro-reward circuit activated by drugs of abuse such as [[heroin]] and [[cocaine]]. This suggests nicotine use has a pleasurable effect that triggers positive reinforcement.<ref>[http://www.nida.nih.gov/MOM/TG/momtg-nicotine.html Nicotine and the Brain]</ref> One study found that smokers exhibit better reaction-time and memory performance compared to non-smokers, which is consistent with increased activation of dopamine receptors.<ref>[http://www.springerlink.com/content/f6gxhlj63peeytlr/ The effects of cigarette smoking on overnight performance]</ref> Neurologically, rodent studies have found that nicotine self-administration causes lowering of reward thresholds—a finding opposite that of most other drugs of abuse (e.g. cocaine and heroin). This increase in reward circuit sensitivity persisted months after the self-administration ended, suggesting that nicotine's alteration of brain reward function is either long lasting or permanent. Furthermore, it has been found that nicotine can activate long term potentiation ''in vivo'' and ''in vitro''. These studies suggests nicotine’s "trace memory" may contribute to difficulties in nicotine abstinence.
Recent evidence has shown that smoking tobacco increases the release of [[dopamine]] in the brain, specifically in the mesolimbic pathway, the same neuro-reward circuit activated by drugs of abuse such as [[heroin]] and [[cocaine]]. This suggests nicotine use has a pleasurable effect that triggers positive reinforcement.<ref>[http://www.nida.nih.gov/MOM/TG/momtg-nicotine.html Nicotine and the Brain]</ref> One study found that smokers exhibit better reaction-time and memory performance compared to non-smokers, which is consistent with increased activation of dopamine receptors.<ref>[http://www.springerlink.com/content/f6gxhlj63peeytlr/ The effects of cigarette smoking on overnight performance]</ref> Neurologically, rodent studies have found that nicotine self-administration causes lowering of reward thresholds—a finding opposite that of most other drugs of abuse (e.g. cocaine and heroin). This increase in reward circuit sensitivity persisted months after the self-administration ended, suggesting that nicotine's alteration of brain reward function is either long lasting or permanent. Furthermore, it has been found that nicotine can activate long term potentiation ''in vivo'' and ''in vitro''. These studies suggests nicotine’s "trace memory" may contribute to difficulties in nicotine abstinence.


The carcinogenity of tobacco smoke is not explained by [[nicotine]] per se, which is not carcinogenic or mutagenic. However, it inhibits [[apoptosis]], therefore accelerating existing cancers.<ref>{{cite journal|author=Maneckjee, R|title=Opioids induce while nicotine suppresses apoptosis in human lung cancer cells|journal=Cell Growth and Differentiation: the Molecular Biology Journal of the American Association of Cancer Research|volume=5|issue=10|pages=1033–1040|year=1994|pmid=7848904 }}</ref> Also, [[NNK]], a nicotine derivative converted from nicotine, can be carcinogenic.
The carcinogenity of tobacco smoke is not explained by [[nicotine]] per se, which is not carcinogenic or mutagenic. However, it inhibits [[apoptosis]], therefore accelerating existing cancers.<ref>{{Cite pmid|7848904}}</ref> Also, [[NNK]], a nicotine derivative converted from nicotine, can be carcinogenic.


It is worth noting that [[nicotine]], although frequently implicated in producing [[tobacco]] addiction, is not significantly addictive when administered alone.<ref name="pmid16177026">{{cite journal |author=Guillem K, Vouillac C, Azar MR, ''et al.'' |title=Monoamine oxidase inhibition dramatically increases the motivation to self-administer nicotine in rats |journal=J. Neurosci. |volume=25 |issue=38 |pages=8593–600 |year=2005 |month=September |pmid=16177026 |doi=10.1523/JNEUROSCI.2139-05.2005 |url=}}</ref> The addictive potential manifests itself after co-administration of an [[MAOI]], which specifically causes [[sensitization]] of the [[locomotor system|locomotor]] response in rats, a measure of addictive potential.<ref name="pmid14592678">{{cite journal |author=Villégier AS, Blanc G, Glowinski J, Tassin JP |title=Transient behavioral sensitization to nicotine becomes long-lasting with monoamine oxidases inhibitors |journal=Pharmacol. Biochem. Behav. |volume=76 |issue=2 |pages=267–74 |year=2003 |month=September |pmid=14592678 |doi= |url=}}</ref>
It is worth noting that [[nicotine]], although frequently implicated in producing [[tobacco]] addiction, is not significantly addictive when administered alone.<ref name="pmid16177026">{{Cite doi|10.1523/JNEUROSCI.2139-05.2005}}</ref> The addictive potential manifests itself after co-administration of an [[MAOI]], which specifically causes [[sensitization]] of the [[locomotor system|locomotor]] response in rats, a measure of addictive potential.<ref name="pmid14592678">{{Cite pmid|14592678}}</ref>


===Genetic===
===Genetic===


According to three separate studies commissioned by governments in the US and Europe, scientists have identified a genetic link that makes people more likely to become addicted to tobacco. This genetic variation causes individuals to smoke more cigarettes, makes it harder for them to quit and increases their likelihood of developing lung cancer by up to 80%.<ref> [http://news.yahoo.com/s/ap/20080402/ap_on_he_me/smokers_genes;_ylt=Ak4zQnOQ3En2NHj69NZnx.Ks0NUE]</ref>
According to three separate studies commissioned by governments in the US and Europe, scientists have identified a genetic link that makes people more likely to become addicted to tobacco. This genetic variation causes individuals to smoke more cigarettes, makes it harder for them to quit and increases their likelihood of developing lung cancer by up to 80%.<ref>[http://news.yahoo.com/s/ap/20080402/ap_on_he_me/smokers_genes;_ylt=Ak4zQnOQ3En2NHj69NZnx.Ks0NUE]</ref>


Genetic markers of more than 35,000 people (mostly smokers and ex-smokers) were surveyed by scientists in three separate studies, and all three found lung cancer to be associated with similar sets of genetic differences. The genetic variations of note encode nicotine receptors on cells and were identified on a region of chromosome 15.<ref>[http://www.nature.com/news/2008/080402/full/news.2008.733.html Access : Genetic link for lung cancer identified : Nature News<!-- Bot generated title -->]</ref> Possessing a single copy of the mutation raises an individual's risk of lung cancer by approximately 30%; for two copies the increase is about 80%. The gene was found to be attributable to 14% of lung cancer cases, and it was found to confer similar lung cancer risks irrespective of smoking status or quantity smoked.<ref name=pmid18385738>{{cite journal|author=Hung RJ, MacKay JD|title=A susceptibility locus for lung cancer maps to nicotinic acetylcholine receptor subunit genes on 15q25|journal=Nature|volume=452|issue=7187|pages=633–7|year=2008|pmid=18385738}}</ref>
Genetic markers of more than 35,000 people (mostly smokers and ex-smokers) were surveyed by scientists in three separate studies, and all three found lung cancer to be associated with similar sets of genetic differences. The genetic variations of note encode nicotine receptors on cells and were identified on a region of chromosome 15.<ref>[http://www.nature.com/news/2008/080402/full/news.2008.733.html Access : Genetic link for lung cancer identified : Nature News<!-- Bot generated title -->]</ref> Possessing a single copy of the mutation raises an individual's risk of lung cancer by approximately 30%; for two copies the increase is about 80%. The gene was found to be attributable to 14% of lung cancer cases, and it was found to confer similar lung cancer risks irrespective of smoking status or quantity smoked.<ref name=pmid18385738>{{Cite pmid|18385738}}</ref>


Another study related to genetic changes in smokers was conducted by Wan L Lam and Stephen Lam from the BC Cancer Agency, in 2007. The study revealed that cigarette smoke can turn on or off some of the genes, which otherwise would remain inactive. Some changes on genetic level could be reversed after the smoking was quit, yet others could not. Examples of reversible genes involved the so-called xenofobic functions, nucleotide metabolism and mucus secretion. Smoking turns off some DNA repair genes that cannot be reversed. It also switches off permanently some genes responsible from protection from cancer growth in the body.<ref>{{cite news|title=Genes Permanently Turned On by Smoking|url=http://www.infoniac.com/health-fitness/genes-permanently-turned-on-by-smoking.html|accessdate=2009-01-14|publisher=InfoNIAC.com}}</ref>
Another study related to genetic changes in smokers was conducted by Wan L Lam and Stephen Lam from the BC Cancer Agency, in 2007. The study revealed that cigarette smoke can turn on or off some of the genes, which otherwise would remain inactive. Some changes on genetic level could be reversed after the smoking was quit, yet others could not. Examples of reversible genes involved the so-called xenofobic functions, nucleotide metabolism and mucus secretion. Smoking turns off some DNA repair genes that cannot be reversed. It also switches off permanently some genes responsible from protection from cancer growth in the body.<ref>{{Cite news|title=Genes Permanently Turned On by Smoking|url=http://www.infoniac.com/health-fitness/genes-permanently-turned-on-by-smoking.html|accessdate=2009-01-14|publisher=InfoNIAC.com}}</ref>


==Health effects==
==Health effects==
{{Copyedit|date=December 2008}}
{{Copyedit|date=December 2008}}
[[Image:Smokingheltheffect.gif|thumb|right|Summary of tobacco related diseases. ''Click to enlarge'']]
[[File:Smokingheltheffect.gif|thumb|right|Summary of tobacco related diseases. ''Click to enlarge'']]


Most scientists involved in cancer research believe that the environmental factors, which include anything the people interact with such as lifestyle choices, their diet, natural and medical radiation, sunlight exposure, workplace exposure, and socioeconomic factors that affect exposures and susceptibility—may be a major contributor to the development of cancer.<ref>[[#Lichtenstein2000|Lichtenstein]] (2000), pp. 78–85.</ref> Other factors that play a major role in cancer development are infectious diseases, aging, and individual susceptibility such as genetic predisposition.<ref>[[#Montesano2001|Montesano]] (2001), pp. 67-87.</ref> Because of these confounding variables, it is difficult to distinguish which factor or condition contributes to the development of cancer. For example, smoking tobacco is known to cause cancer in humans, but not all people who smoke develop smoking-related cancer; however, with some substances or exposure circumstances, cancer may develop after even brief exposure.<ref>[http://ntp.niehs.nih.gov/ntp/roc/eleventh/intro.pdf 11th ROC: Introduction<!-- Bot generated title -->]</ref>
Most scientists involved in cancer research believe that the environmental factors, which include anything the people interact with such as lifestyle choices, their diet, natural and medical radiation, sunlight exposure, workplace exposure, and socioeconomic factors that affect exposures and susceptibility—may be a major contributor to the development of cancer.<ref>[[#Lichtenstein2000|Lichtenstein]] (2000), pp. 78–85.</ref> Other factors that play a major role in cancer development are infectious diseases, aging, and individual susceptibility such as genetic predisposition.<ref>[[#Montesano2001|Montesano]] (2001), pp. 67-87.</ref> Because of these confounding variables, it is difficult to distinguish which factor or condition contributes to the development of cancer. For example, smoking tobacco is known to cause cancer in humans, but not all people who smoke develop smoking-related cancer; however, with some substances or exposure circumstances, cancer may develop after even brief exposure.<ref>[http://ntp.niehs.nih.gov/ntp/roc/eleventh/intro.pdf 11th ROC: Introduction<!-- Bot generated title -->]</ref>
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A person's increased risk of contracting disease is directly proportional to the length of time that a person continues to smoke as well as the amount smoked. However, if someone stops smoking, then these chances gradually decrease as the damage to their body is repaired. A year after quitting, the risk of contracting heart disease is half that of a continuing smoker.<ref>[http://www.americanheart.org/presenter.jhtml?identifier=4735 "Smoking Cessation Guidelines"] American Heart Foundation</ref> The health risks of smoking are not uniform across all smokers. Risks vary according to amount of tobacco smoked, with those who smoke more at greater risk. Light smoking is still a health risk. Likewise, smoking "light" cigarettes does not reduce the risks.
A person's increased risk of contracting disease is directly proportional to the length of time that a person continues to smoke as well as the amount smoked. However, if someone stops smoking, then these chances gradually decrease as the damage to their body is repaired. A year after quitting, the risk of contracting heart disease is half that of a continuing smoker.<ref>[http://www.americanheart.org/presenter.jhtml?identifier=4735 "Smoking Cessation Guidelines"] American Heart Foundation</ref> The health risks of smoking are not uniform across all smokers. Risks vary according to amount of tobacco smoked, with those who smoke more at greater risk. Light smoking is still a health risk. Likewise, smoking "light" cigarettes does not reduce the risks.


Tobacco use most commonly leads to diseases affecting the heart and [[respiratory system|lungs]], with smoking being a major risk factor for [[myocardial infarction|heart attacks]], [[Chronic Obstructive Pulmonary Disease]] (COPD), [[emphysema]], and [[cancer]], particularly [[lung cancer]], cancers of the [[larynx]] and [[mouth]], and [[pancreatic cancer]]. Overall life expectancy is also reduced in regular smokers, with estimates ranging from 10<ref name="pmid15213107">{{cite journal|author=Doll R, Peto R, Boreham J, Sutherland I|title=Mortality in relation to smoking: 50 years' observations on male British doctors|journal=BMJ|volume=328|issue=7455|page=1519|year=2004|pmid=15213107|doi=10.1136/bmj.38142.554479.AE}}</ref> to 17.9 <ref>Contingencies May-June 1990. http://tobaccodocuments.org/ti/TIMN0020615-0620.html
Tobacco use most commonly leads to diseases affecting the heart and [[respiratory system|lungs]], with smoking being a major risk factor for [[myocardial infarction|heart attacks]], [[Chronic Obstructive Pulmonary Disease]] (COPD), [[emphysema]], and [[cancer]], particularly [[lung cancer]], cancers of the [[larynx]] and [[mouth]], and [[pancreatic cancer]]. Overall life expectancy is also reduced in regular smokers, with estimates ranging from 10<ref name="pmid15213107">{{Cite doi|10.1136/bmj.38142.554479.AE}}</ref> to 17.9 <ref>Contingencies May-June 1990. http://tobaccodocuments.org/ti/TIMN0020615-0620.html
</ref> years fewer than nonsmokers.<ref name="pmid10192312">{{cite journal|author=Ferrucci L, Izmirlian G, Leveille S, ''et al.''|title=Smoking, physical activity, and active life expectancy|journal=Am. J. Epidemiol.|volume=149|issue=7|pages=645–53|year=1999|pmid=10192312}}</ref> About two thirds of male smokers will die of illness due to smoking.<ref name="pmid7755693">{{cite journal|author=Doll R, Peto R, Wheatley K, Gray R, Sutherland I|title=Mortality in relation to smoking: 40 years' observations on male British doctors|journal=BMJ|volume=309|issue=6959|pages=901–11|year=1994|pmid=7755693}}</ref> The association of smoking with lung cancer is strongest, both in the public perception and etiologically. People who have smoked tobacco at some point have about a one in ten chance of developing lung cancer during their lifetime.<ref>{{cite web|title=Lung Cancer Suscepitibility and Outcomes study|publisher=Harvard School of Public Health|author=David C. Christiani|url=http://www.hsph.harvard.edu/lungcancer/|accessdate=2009-01-03}}</ref> If one looks at men who continue to smoke tobacco, the risk increases to one in six.<ref name="pmid7895211">{{cite journal|author=Villeneuve PJ, Mao Y|title=Lifetime probability of developing lung cancer, by smoking status, Canada|journal=Canadian journal of public health. Revue canadienne de santé publique|volume=85|issue=6|pages=385–8|year=1994|pmid=7895211}}</ref> Historically, lung cancer was considered to be a rare disease prior to [[World War I]] and was perceived as something most physicians would never see during their career. With the postwar rise in popularity of cigarette smoking came a virtual epidemic of lung cancer.<ref>{{cite journal|author=Witschi H|title=A short history of lung cancer|journal=Toxicol. Sci.|volume=64|issue=1|pages=4–6|year=2001|month=November|pmid=11606795|url=http://toxsci.oxfordjournals.org/cgi/pmidlookup?view=long&pmid=11606795}}</ref><ref>Adler I. Primary malignant growths of the lungs and bronchi. New York: Longmans, Green, and Company; 1912., cited in {{cite journal|author=Spiro SG, Silvestri GA|title=One hundred years of lung cancer|journal=Am. J. Respir. Crit. Care Med.|volume=172|issue=5|pages=523–9|year=2005|month=September|pmid=15961694|doi=10.1164/rccm.200504-531OE}}</ref>
</ref> years fewer than nonsmokers.<ref name="pmid10192312">{{Cite pmid|10192312}}</ref> About two thirds of male smokers will die of illness due to smoking.<ref name="pmid7755693">{{Cite pmid|7755693}}</ref> The association of smoking with lung cancer is strongest, both in the public perception and etiologically. People who have smoked tobacco at some point have about a one in ten chance of developing lung cancer during their lifetime.<ref>{{Cite web|title=Lung Cancer Suscepitibility and Outcomes study|publisher=Harvard School of Public Health|author=David C. Christiani|url=http://www.hsph.harvard.edu/lungcancer/|accessdate=2009-01-03}}</ref> If one looks at men who continue to smoke tobacco, the risk increases to one in six.<ref name="pmid7895211">{{Cite pmid|7895211}}</ref> Historically, lung cancer was considered to be a rare disease prior to [[World War I]] and was perceived as something most physicians would never see during their career. With the postwar rise in popularity of cigarette smoking came a virtual epidemic of lung cancer.<ref>{{Cite pmid|11606795}}</ref><ref>Adler I. Primary malignant growths of the lungs and bronchi. New York: Longmans, Green, and Company; 1912., cited in {{Cite doi|10.1164/rccm.200504-531OE}}</ref>


A person's increased risk of contracting disease is directly proportional to the length of time that a person smokes, as well as to the amount smoked, and doctors use the approximation "[[pack years]]" in assessing the likelihood of smoking-related illness. However, if someone stops smoking, then their risk declines over time,<ref name=NCI_quit /> and the reduction in their [[lung function]] will stop.
A person's increased risk of contracting disease is directly proportional to the length of time that a person smokes, as well as to the amount smoked, and doctors use the approximation "[[pack years]]" in assessing the likelihood of smoking-related illness. However, if someone stops smoking, then their risk declines over time,<ref name=NCI_quit /> and the reduction in their [[lung function]] will stop.
Line 113: Line 109:
Male and female smokers lose an average of 13.2 and 14.5 years of life, respectively.<ref>MMWR April 12, 2002 / 51(14);300-3</ref>
Male and female smokers lose an average of 13.2 and 14.5 years of life, respectively.<ref>MMWR April 12, 2002 / 51(14);300-3</ref>


According to the results of a 50 year study of 34,439 male British doctors, at least half of all lifelong smokers die earlier as a result of smoking.<ref>BMJ, doi:10.1136/bmj.38142.554479.AE (published 22 June 2004)[[File:50 ycs.pdf]]</ref>
According to the results of a 50 year study of 34,439 male British doctors, at least half of all lifelong smokers die earlier as a result of smoking.<ref>{{Cite doi|10.1136/bmj.38142.554479.AE}}</ref>


Smokers are triple as likely of dying before the age of 70.<ref>18European Heart Journal 2004 25(5):409-415; doi:10.1016/j.ehj.2003.12.015</ref><ref>BMJ 328 (1519): 1519. doi:10.1136/bmj.38142.554479.AE. PMID 15213107</ref><ref>American Journal of Public Health p.1223</ref>
Smokers are triple as likely of dying before the age of 70.<ref>{{Cite doi|10.1016/j.ehj.2003.12.015}}</ref><ref>{{Cite pmid|15213107}}</ref><ref>American Journal of Public Health p.1223</ref>


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In the United States alone, cigarette smoking and exposure to tobacco smoke results in at least 443,000 premature deaths annually.<ref>MMWR November 14, 2008 / 57(45);1226-1228</ref>
In the United States alone, cigarette smoking and exposure to tobacco smoke results in at least 443,000 premature deaths annually.<ref>MMWR November 14, 2008 / 57(45);1226-1228</ref>


In the United States alone, tobacco kills the equivalent of three jumbo jets full of people crashing every day, with no survivors, 365 days of the year. -ABC's Peter Jennings<ref> Never Say Die, an ABC News special by [[Peter Jennings]] 6/27/1996</ref> On a worldwide basis, it's 1 jumbo jet per hour, 24 hours a day, 365 days of the year. -WHO <ref>http://ws.missouristate.edu/breatheeasymo/upload/Newsletters/Newsletter62.pdf</ref>
In the United States alone, tobacco kills the equivalent of three jumbo jets full of people crashing every day, with no survivors, 365 days of the year. -ABC's Peter Jennings<ref>Never Say Die, an ABC News special by [[Peter Jennings]] 6/27/1996</ref> On a worldwide basis, it's 1 jumbo jet per hour, 24 hours a day, 365 days of the year. -WHO <ref>http://ws.missouristate.edu/breatheeasymo/upload/Newsletters/Newsletter62.pdf</ref>


===Cancer===
===Cancer===
The primary risks of tobacco usage include many forms of cancer, particularly [[lung cancer]],<ref>[[American Legacy Foundation]] [http://www.americanlegacy.org/PDF/Lung_Cancer_Fact_Sheet.pdf factsheet on lung cancer]; their cited source is: <u>CDC ([[Centers for Disease Control]]) The Health Consequences of Smoking: A Report of the Surgeon General. 2004</u>.</ref> [[renal cell carcinoma|cancer of the kidney]],<ref>{{cite journal|author=Lipworth L, Tarone RE, McLaughlin JK|title=The epidemiology of renal cell carcinoma|journal=J. Urol.|volume=176|issue=6 Pt 1|pages=2353–8|year=2006|month=December|pmid=17085101|doi=10.1016/j.juro.2006.07.130}}</ref> [[cancer of the larynx]] and head and neck, [[breast cancer]],<ref>{{cite journal|author=Cui Y, Miller AB, Rohan TE|title=Cigarette smoking and breast cancer risk: update of a prospective cohort study|journal=Breast Cancer Res. Treat.|volume=100|issue=3|pages=293–9|year=2006|month=December|pmid=16773435|doi=10.1007/s10549-006-9255-3}}</ref><ref>{{cite journal|author=Calle EE, Miracle-McMahill HL, Thun MJ, Heath CW|title=Cigarette smoking and risk of fatal breast cancer|journal=Am. J. Epidemiol.|volume=139|issue=10|pages=1001–7|year=1994|month=May|pmid=8178779|url=http://aje.oxfordjournals.org/cgi/pmidlookup?view=long&pmid=8178779}}</ref> [[bladder cancer|bladder]],<ref>{{cite journal|author=Boffetta P|title=Tobacco smoking and risk of bladder cancer|journal=Scand J Urol Nephrol Suppl|volume=42|issue=S218|pages=45–54|year=2008|pmid=18815916|doi=10.1080/03008880802283664}}</ref> [[esophageal cancer|esophagus]], [[pancreatic cancer|pancreas]],<ref>{{cite journal|journal=Langenbecks Arch Surg|year=2008|title=Tobacco and the risk of pancreatic cancer: a review and meta-analysis|author=Iodice S, Gandini S, Maisonneuve P, Lowenfels AB|doi=10.1007/s00423-007-0266-2|pmid=18193270|volume=393|page=535}}</ref> and [[gastric carcinoma|stomach]].<ref>{{cite journal|author=Kuper H, Boffetta P, Adami HO|title=Tobacco use and cancer causation: association by tumour type|journal=J. Intern. Med.|volume=252|issue=3|pages=206–24|year=2002|month=September|pmid=12270001|url=http://www.blackwell-synergy.com/openurl?genre=article&sid=nlm:pubmed&issn=0954-6820&date=2002&volume=252&issue=3&spage=206}}</ref> There is some evidence suggesting an increased risk of [[myeloid leukemia]], squamous cell sinonasal cancer, [[Hepatocellular carcinoma|liver cancer]], [[cervical cancer]], [[colorectal cancer]] after an extended latency, childhood cancers and cancers of the [[gall bladder]], [[adrenal gland]] and [[small intestine]].
The primary risks of tobacco usage include many forms of cancer, particularly [[lung cancer]],<ref>[[American Legacy Foundation]] [http://www.americanlegacy.org/PDF/Lung_Cancer_Fact_Sheet.pdf factsheet on lung cancer]; their cited source is: <u>CDC ([[Centers for Disease Control]]) The Health Consequences of Smoking: A Report of the Surgeon General. 2004</u>.</ref> [[renal cell carcinoma|cancer of the kidney]],<ref>{{Cite doi|10.1016/j.juro.2006.07.130}}</ref> [[cancer of the larynx]] and head and neck, [[breast cancer]],<ref>{{Cite doi|10.1007/s10549-006-9255-3}}</ref><ref>{{Cite pmid|8178779}}</ref> [[bladder cancer|bladder]],<ref>{{Cite doi|10.1080/03008880802283664}}</ref> [[esophageal cancer|esophagus]], [[pancreatic cancer|pancreas]],<ref>{{Cite doi|10.1007/s00423-007-0266-2}}</ref> and [[gastric carcinoma|stomach]].<ref>{{Cite pmid|12270001}}</ref> There is some evidence suggesting an increased risk of [[myeloid leukemia]], squamous cell sinonasal cancer, [[Hepatocellular carcinoma|liver cancer]], [[cervical cancer]], [[colorectal cancer]] after an extended latency, childhood cancers and cancers of the [[gall bladder]], [[adrenal gland]] and [[small intestine]].


====Lung Cancer====
====Lung Cancer====
The risk of dying from lung
The risk of dying from lung
cancer before age 85 is 22.1% for a male smoker and 11.9% for a female current smoker, in the absence of competing causes of death. The corresponding estimates for lifelong nonsmokers are a 1.1% probability of dying from lung cancer before age 85 for a man of European descent, and a 0.8% probability for a woman\<ref>{{Cite doi|10.1371/journal.pmed.0050185}}</ref>
cancer before age 85 is 22.1% for a male smoker and
11.9% for a female current smoker, in the absence of
competing causes of death. The corresponding estimates for
lifelong nonsmokers are a 1.1% probability of dying from
lung cancer before age 85 for a man of European descent, and
a 0.8% probability for a woman<ref>Thun MJ, Hannan LM, Adams-
Campbell LL, Boffetta P, Buring JE, et al.
(2008) Lung cancer occurrence in
never-smokers: An analysis of 13
cohorts and 22 cancer registry studies.
PLoS Med 5(9): e185. doi:10.1371/
journal.pmed.0050185</ref>.


===Pulmonary===
===Pulmonary===


[[Image:Cancer smoking lung cancer correlation from NIH.svg|frame|right|Since establishing causation through experimental trials was not possible due to ethical restrictions, a lengthy study was conducted in order to establish the strong association necessary to allow for legislative action against tobacco consumption.{{Citation needed|date=May 2009}}]]
[[File:Cancer smoking lung cancer correlation from NIH.svg|frame|right|Since establishing causation through experimental trials was not possible due to ethical restrictions, a lengthy study was conducted in order to establish the strong association necessary to allow for legislative action against tobacco consumption.{{Citation needed|date=May 2009}}]]


In smoking, long term exposure to compounds found in the smoke such as [[carbon monoxide]], [[cyanide]], and so forth—, are believed to be responsible for pulmonary damage and for loss of elasticity in the [[alveoli]], leading to emphysema and COPD. The carcinogen acrolein and its derivatives also contribute to the chronic inflammation present in COPD.<ref name="Facchinetti">Facchinetti et al. α,β-Unsaturated Aldehydes in Cigarette Smoke Release Inflammatory Mediators from Human Macrophages. American Journal of Respiratory Cell and Molecular Biology. Vol. 37, pp. 617-623, 2007. DOI: 10.1165/rcmb.2007-0130OC</ref>
In smoking, long term exposure to compounds found in the smoke such as [[carbon monoxide]], [[cyanide]], and so forth—, are believed to be responsible for pulmonary damage and for loss of elasticity in the [[alveoli]], leading to emphysema and COPD. The carcinogen acrolein and its derivatives also contribute to the chronic inflammation present in COPD.<ref name="Facchinetti">{{Cite doi|10.1165/rcmb.2007-0130OC}}</ref>


Secondhand smoke is a mixture of smoke from the burning end of a cigarette, pipe or cigar and the smoke exhaled from the lungs of smokers. It is involuntarily inhaled, lingers in the air hours after cigarettes have been extinguished, and can cause a wide range of adverse health effects, including cancer, respiratory infections, and asthma.<ref name="ALASecondhandSmokeFactSheet">[http://www.lungusa.org/site/pp.asp?c=dvLUK9O0E&b=35422#one "Secondhand Smoke Fact Sheet", ''American Lung Association''] June 2007.</ref> Nonsmokers who are exposed to secondhand smoke at home or work increase their heart disease risk by 25–30% and their lung cancer risk by 20–30%. Secondhand smoke has been estimated to cause 38,000 deaths per year, of which 3,400 are deaths from lung cancer in non-smokers.<ref>[http://www.tobaccofreefloridanewsroom.com/?cat=6 "Tobacco-Free Florida", ''Centers for Disease Control & Prevention Fact Sheets'']</ref>
Secondhand smoke is a mixture of smoke from the burning end of a cigarette, pipe or cigar and the smoke exhaled from the lungs of smokers. It is involuntarily inhaled, lingers in the air hours after cigarettes have been extinguished, and can cause a wide range of adverse health effects, including cancer, respiratory infections, and asthma.<ref name="ALASecondhandSmokeFactSheet">[http://www.lungusa.org/site/pp.asp?c=dvLUK9O0E&b=35422#one "Secondhand Smoke Fact Sheet", ''American Lung Association''] June 2007.</ref> Nonsmokers who are exposed to secondhand smoke at home or work increase their heart disease risk by 25–30% and their lung cancer risk by 20–30%. Secondhand smoke has been estimated to cause 38,000 deaths per year, of which 3,400 are deaths from lung cancer in non-smokers.<ref>[http://www.tobaccofreefloridanewsroom.com/?cat=6 "Tobacco-Free Florida", ''Centers for Disease Control & Prevention Fact Sheets'']</ref>


[[Chronic obstructive pulmonary disease]] (COPD) caused by smoking, known as tobacco disease, is a permanent, incurable reduction of pulmonary capacity characterized by shortness of breath, wheezing, persistent cough with [[sputum]], and damage to the lungs, including [[emphysema]] and [[chronic bronchitis]].<ref>{{cite journal|author=Devereux G|title=ABC of chronic obstructive pulmonary disease. Definition, epidemiology, and risk factors.|journal=BMJ|year=2006|volume=332|pages=1142–1144|pmid=16690673|doi=10.1136/bmj.332.7550.1142}}</ref>
[[Chronic obstructive pulmonary disease]] (COPD) caused by smoking, known as tobacco disease, is a permanent, incurable reduction of pulmonary capacity characterized by shortness of breath, wheezing, persistent cough with [[sputum]], and damage to the lungs, including [[emphysema]] and [[chronic bronchitis]].<ref>{{Cite doi|10.1136/bmj.332.7550.1142}}</ref>


===Influenza===
===Influenza===
A study of an outbreak of A(H1N1) influenza in an Israeli military unit of 336 healthy young men to determine the relation of cigarette smoking to the incidence of clinically apparent influenza, revealed that, of 168 smokers, 68.5 percent had influenza, as compared with 47.2 percent of nonsmokers. Influenza was also more severe in the smokers; 50.6 percent of the smokers lost work days or required bed rest, or both, as compared with 30.1 percent of the nonsmokers<ref name="content.nejm.org">http://content.nejm.org/content/vol307/issue17/index.dtl</ref>.
A study of an outbreak of A(H1N1) influenza in an Israeli military unit of 336 healthy young men to determine the relation of cigarette smoking to the incidence of clinically apparent influenza, revealed that, of 168 smokers, 68.5 percent had influenza, as compared with 47.2 percent of nonsmokers. Influenza was also more severe in the smokers; 50.6 percent of the smokers lost work days or required bed rest, or both, as compared with 30.1 percent of the nonsmokers<ref name="content.nejm.org">http://content.nejm.org/content/vol307/issue17/index.dtl</ref>.
According to a study of 1,900 male cadets after the 1968 Hong Kong A2 influenza epidemic at a South Carolina military academy, compared with nonsmokers heavy smokers (more than 20 cigarettes per day), had 21% more illnesses and 20% more bed rest, light smokers (less than 20 cigarettes per day) had 10% more illnesses and 7% more bed rest<ref>Finklea et al. 1969</ref>.
According to a study of 1,900 male cadets after the 1968 Hong Kong A2 influenza epidemic at a South Carolina military academy, compared with nonsmokers heavy smokers (more than 20 cigarettes per day), had 21% more illnesses and 20% more bed rest, light smokers (less than 20 cigarettes per day) had 10% more illnesses and 7% more bed rest<ref>Finklea et al. 1969</ref>.


The effect of cigarette smoking upon epidemic influenza was studied prospectively among 1,811 male college students. Clinical influenza incidence among those who daily smoked 21 or more cigarettes was 21% higher than that of non-smokers. Influenza incidence among smokers of 1 to 20 cigarettes daily was intermediate between non-smokers and heavy cigarette smokers<ref>Finklea, J. F., S. H. Sandifer and D. D. Smith. Cigarette smoking and epidemic influenza. Amer. J. Epid., 90: 390–399.—</ref>.
The effect of cigarette smoking upon epidemic influenza was studied prospectively among 1,811 male college students. Clinical influenza incidence among those who daily smoked 21 or more cigarettes was 21% higher than that of non-smokers. Influenza incidence among smokers of 1 to 20 cigarettes daily was intermediate between non-smokers and heavy cigarette smokers<ref>Finklea, J. F., S. H. Sandifer and D. D. Smith. Cigarette smoking and epidemic influenza. Amer. J. Epid., 90: 390–399.—</ref>.


Surveillance of a 1979 influenza out-break at a military base for women in Israel revealed that, Influenza symptoms developed in 60.0% of the current smokers vs. 41.6% of the nonsmokers<ref>Kark and Lebiush American Journal of Public Health, Vol. 71, Issue 5 530-532 1981</ref>.
Surveillance of a 1979 influenza out-break at a military base for women in Israel revealed that, Influenza symptoms developed in 60.0% of the current smokers vs. 41.6% of the nonsmokers<ref>Kark and Lebiush American Journal of Public Health, Vol. 71, Issue 5 530-532 1981</ref>.


Smoking seems to cause a higher relative influenza-risk in older populations than in younger populations. In a prospective study of community-dwelling people 60–90 years of age, during 1993, of unimmunized people 23% of smokers had clinical influenza as compared with 6 % of non-smokers<ref>Epidemiology and Infection (1999), 123:1:103-108 Cambridge University Press</ref>.
Smoking seems to cause a higher relative influenza-risk in older populations than in younger populations. In a prospective study of community-dwelling people 60–90 years of age, during 1993, of unimmunized people 23% of smokers had clinical influenza as compared with 6 % of non-smokers<ref>Epidemiology and Infection (1999), 123:1:103-108 Cambridge University Press</ref>.


Smoking may substantially contribute to the growth of influenza epidemics affecting the entire population<ref name="content.nejm.org"/>. However the proportion of influenza cases in the general non-smoking population attributable to smokers has not yet been calculated.
Smoking may substantially contribute to the growth of influenza epidemics affecting the entire population<ref name="content.nejm.org"/>. However the proportion of influenza cases in the general non-smoking population attributable to smokers has not yet been calculated.


===Cardiovascular===
===Cardiovascular===


Inhalation of tobacco smoke causes several immediate responses within the heart and blood vessels. Within one minute the heart rate begins to rise, increasing by as much as 30 percent during the first 10 minutes of smoking. Carbon monoxide in tobacco smoke exerts its [[carbon monoxide poisoning|negative effects]] by reducing the blood’s ability to carry oxygen.<ref>{{cite journal|author=Haldane J|year=1895|title=The action of carbonic oxide on man|journal=J Physiol|volume=18|pages=430–462}}</ref>
Inhalation of tobacco smoke causes several immediate responses within the heart and blood vessels. Within one minute the heart rate begins to rise, increasing by as much as 30 percent during the first 10 minutes of smoking. Carbon monoxide in tobacco smoke exerts its [[carbon monoxide poisoning|negative effects]] by reducing the blood’s ability to carry oxygen.<ref>{{Cite journal|author=Haldane J|year=1895|title=The action of carbonic oxide on man|journal=J Physiol|volume=18|pages=430–462}}</ref>


Smoking also increases the chance of [[heart disease]], [[stroke]], [[atherosclerosis]], and [[peripheral vascular disease]]. Several ingredients of tobacco lead to the narrowing of blood vessels, increasing the likelihood of a blockage, and thus a [[myocardial infarction|heart attack]] or [[stroke]]. According to a study by an international team of researchers, people under 40 are five times more likely to have a heart attack if they smoke.<ref name="news.bbc.co.uk.330">{{cite news|title=Health : Young smokers' heart attack risk|url=http://news.bbc.co.uk/2/hi/health/3590320.stm|accessdate=2005-12-18|publisher=BBC }}</ref>
Smoking also increases the chance of [[heart disease]], [[stroke]], [[atherosclerosis]], and [[peripheral vascular disease]]. Several ingredients of tobacco lead to the narrowing of blood vessels, increasing the likelihood of a blockage, and thus a [[myocardial infarction|heart attack]] or [[stroke]]. According to a study by an international team of researchers, people under 40 are five times more likely to have a heart attack if they smoke.<ref name="news.bbc.co.uk.330">{{Cite news|title=Health : Young smokers' heart attack risk|url=http://news.bbc.co.uk/2/hi/health/3590320.stm|accessdate=2005-12-18|publisher=BBC }}</ref>


Latest research of the American biologists have determined that cigarette smoke also influences the process of cell division in the cardiac muscle and changes heart's shape.<ref name="InfoNIAC.com">{{cite news|title=Cigarette Smoke Changes Heart's Shape|url=http://www.infoniac.com/health-fitness/cigarette-smoke-changes-heart-s-shape.html|accessdate=2009-01-10|publisher=InfoNIAC.com }}</ref>
Latest research of the American biologists have determined that cigarette smoke also influences the process of cell division in the cardiac muscle and changes heart's shape.<ref name="InfoNIAC.com">{{Cite news|title=Cigarette Smoke Changes Heart's Shape|url=http://www.infoniac.com/health-fitness/cigarette-smoke-changes-heart-s-shape.html|accessdate=2009-01-10|publisher=InfoNIAC.com }}</ref>


The usage of tobacco has also been linked to [[Buerger's disease]] (''thromboangiitis obliterans'') the acute inflammation and thrombosis (clotting) of arteries and veins of the hands and feet.{{Citation needed|date=December 2008}}
The usage of tobacco has also been linked to [[Buerger's disease]] (''thromboangiitis obliterans'') the acute inflammation and thrombosis (clotting) of arteries and veins of the hands and feet.{{Citation needed|date=December 2008}}
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The current Surgeon General’s Report concluded that there is no risk-free level of exposure to secondhand smoke. Even short exposures to secondhand smoke can cause blood [[platelets]] to become stickier, damage the lining of [[blood vessels]], decrease coronary flow velocity reserves, and reduce heart rate variability, potentially increasing the risk of [[Myocardial infarction|heart attack]]. New research indicates that private research conducted by cigarette company [[Philip Morris International|Philip Morris]] in the 1980s showed that secondhand smoke was toxic, yet the company suppressed the finding during the next two decades.<ref name="ALASecondhandSmokeFactSheet" />
The current Surgeon General’s Report concluded that there is no risk-free level of exposure to secondhand smoke. Even short exposures to secondhand smoke can cause blood [[platelets]] to become stickier, damage the lining of [[blood vessels]], decrease coronary flow velocity reserves, and reduce heart rate variability, potentially increasing the risk of [[Myocardial infarction|heart attack]]. New research indicates that private research conducted by cigarette company [[Philip Morris International|Philip Morris]] in the 1980s showed that secondhand smoke was toxic, yet the company suppressed the finding during the next two decades.<ref name="ALASecondhandSmokeFactSheet" />


Although cigarette smoking causes a greater increase of the risk of cancer than cigar smoking, cigar smokers still have an increased risk for many health problems, including cancer, when compared to non-smokers.<ref name=NCIcigar>{{cite paper|author=David M. Burns, M.D.|title=Cigars: Health Effects and Trends|date=February 1998|url=http://cancercontrol.cancer.gov/tcrb/monographs/9/index.html}}</ref><ref name=Symm>{{cite journal|journal=J Prim Prev|year=2005|volume=26|issue=4|pages=363–75|title=Cigar smoking: an ignored public health threat|author=Symm B, Morgan MV, Blackshear Y, Tinsley S|doi=10.1007/s10935-005-5389-z|pmid=15995804}}</ref> As for Environmental Tobacco Smoke (ETS, or "[[Passive smoking|Second-hand Smoking]]"), the NIH study points to the large amount of smoke generated by one cigar, saying "cigars can contribute substantial amounts of tobacco smoke to the indoor environment; and, when large numbers of cigar smokers congregate together in a cigar smoking event, the amount of ETS produced is sufficient to be a health concern for those regularly required to work in those environments."<ref name=NIH/>
Although cigarette smoking causes a greater increase of the risk of cancer than cigar smoking, cigar smokers still have an increased risk for many health problems, including cancer, when compared to non-smokers.<ref name=NCIcigar>{{Cite paper|author=David M. Burns, M.D.|title=Cigars: Health Effects and Trends|date=February 1998|url=http://cancercontrol.cancer.gov/tcrb/monographs/9/index.html}}</ref><ref name=Symm>{{Cite doi|10.1007/s10935-005-5389-z}}</ref> As for Environmental Tobacco Smoke (ETS, or "[[Passive smoking|Second-hand Smoking]]"), the NIH study points to the large amount of smoke generated by one cigar, saying "cigars can contribute substantial amounts of tobacco smoke to the indoor environment; and, when large numbers of cigar smokers congregate together in a cigar smoking event, the amount of ETS produced is sufficient to be a health concern for those regularly required to work in those environments."<ref name=NIH/>


Smoking tends to increase blood cholesterol levels. Furthermore, the ratio of high-density lipoprotein (the "good" cholesterol) to low-density lipoprotein (the "bad" cholesterol) tends to be lower in smokers compared to non-smokers. Smoking also raises the levels of fibrinogen and increases platelet production (both involved in blood clotting) which makes the blood viscous. Carbon monoxide binds to haemoglobin (the oxygen-carrying component in red blood cells), resulting in a much stabler complex than haemoglobin bound with oxygen or carbon dioxide—the result is permanent loss of blood cell functionality. Blood cells are naturally recycled after a certain period of time, allowing for the creation of new, functional erythrocytes. However, if carbon monoxide exposure reaches a certain point before they can be recycled, hypoxia (and later death) occurs. All these factors make smokers more at risk of developing various forms of arteriosclerosis. As the arteriosclerosis progresses, blood flows less easily through rigid and narrowed blood vessels, making the blood more likely to form a thrombosis (clot). Sudden blockage of a blood vessel may lead to an infarction (e.g. stroke). However, it is also worth noting that the effects of smoking on the heart may be more subtle. These conditions may develop gradually given the smoking-healing cycle (the human body heals itself between periods of smoking), and therefore a smoker may develop less significant disorders such as worsening or maintenance of unpleasant dermatological conditions, e.g. eczema, due to reduced blood supply. Smoking also increases blood pressure and weakens blood vessels.<ref>{{cite journal|author=Narkiewicz K, Kjeldsen SE, Hedner T|title=Is smoking a causative factor of hypertension?|journal=Blood Press.|year=2005|volume=14|issue=2|pages=69–71|pmid=16036482|doi=10.1080/08037050510034202}}</ref>
Smoking tends to increase blood cholesterol levels. Furthermore, the ratio of high-density lipoprotein (the "good" cholesterol) to low-density lipoprotein (the "bad" cholesterol) tends to be lower in smokers compared to non-smokers. Smoking also raises the levels of fibrinogen and increases platelet production (both involved in blood clotting) which makes the blood viscous. Carbon monoxide binds to haemoglobin (the oxygen-carrying component in red blood cells), resulting in a much stabler complex than haemoglobin bound with oxygen or carbon dioxide—the result is permanent loss of blood cell functionality. Blood cells are naturally recycled after a certain period of time, allowing for the creation of new, functional erythrocytes. However, if carbon monoxide exposure reaches a certain point before they can be recycled, hypoxia (and later death) occurs. All these factors make smokers more at risk of developing various forms of arteriosclerosis. As the arteriosclerosis progresses, blood flows less easily through rigid and narrowed blood vessels, making the blood more likely to form a thrombosis (clot). Sudden blockage of a blood vessel may lead to an infarction (e.g. stroke). However, it is also worth noting that the effects of smoking on the heart may be more subtle. These conditions may develop gradually given the smoking-healing cycle (the human body heals itself between periods of smoking), and therefore a smoker may develop less significant disorders such as worsening or maintenance of unpleasant dermatological conditions, e.g. eczema, due to reduced blood supply. Smoking also increases blood pressure and weakens blood vessels.<ref>{{Cite doi|10.1080/08037050510034202}}</ref>


===Oral===
===Oral===


Perhaps the most serious oral condition that can arise is that of [[oral cancer]]. However, smoking also increases the risk for various other oral diseases, some almost completely exclusive to tobacco users. The [[National Institutes of Health]], through the [[National Cancer Institute]], determined in 1998 that "cigar smoking causes a variety of cancers including cancers of the [[oral cancer|oral cavity]] (lip, tongue, mouth, throat), [[Esophageal cancer|esophagus]], [[Laryngeal cancer|larynx]], and [[lung cancer|lung]]."<ref name=NIH>{{cite web|url=http://www.nih.gov/news/pr/apr98/nci-10a.htm|title=Background on Cigar Monograph: Cigars: Health Effects and Trends|date=1998-04-10|accessdate=2008-01-04|author=[[National Institutes of Health]] }}</ref> [[Smoking pipe (tobacco)|Pipe]] smoking involves significant health risks,<ref>{{cite web|url=http://jnci.oxfordjournals.org/cgi/content/full/96/11/853/T2|title=Questions About Smoking, Tobacco, and Health|author=[[American Cancer Society]]|accessdate=2008-01-04}}</ref><ref>{{cite journal|author=Henley SJ, Thun MJ, Chao A, Calle EE|title=Association between exclusive pipe smoking and mortality from cancer and other diseases|journal=J. Natl. Cancer Inst.|volume=96|issue=11|pages=853–61|year=2004|month=June|pmid=15173269|url=http://jnci.oxfordjournals.org/cgi/content/full/96/11/853}}</ref> particularly oral cancer.<ref>{{cite web|url=http://www.ahealthyme.com/topic/pipes|author=Loren Stein|title=Pipe Smoking|publisher=A Healthy Me!|accessdate=2008-01-04}}</ref><ref>{{cite web|url=http://books.nap.edu/openbook.php?record_id=943&page=250|author=Commission on Life Sciences|title=Environmental Tobacco Smoke: Measuring Exposures and Assessing Health Effects (1986)|accessdate=2008-01-04}}</ref> Roughly half of [[periodontitis]] or inflammation around the teeth cases attributed to current or former smoking. Smokeless tobacco causes [[gingival recession]] and white [[mucosal]] [[lesion]]s. Up to 90% of periodontitis patients who are not helped by common modes of treatment are smokers. Smokers have significantly greater loss of bone height than nonsmokers, and the trend can be extend to pipe smokers to have more bone loss than nonsmokers.<ref name="pmid11336116">{{cite journal|journal=J Dent Educ|year=2001|volume=65|issue=4|pages=313–21|title=Impact of tobacco use on periodontal status|author=Johnson GK, Slach NA|pmid=11336116|url=http://www.jdentaled.org/cgi/reprint/65/4/313.pdf|format=PDF|accessdate=2009-06-24}}</ref> Smoking has been proven to be an important factor in the staining of teeth.<ref name="pmid12707498">{{cite journal|author=Reibel J|title=Tobacco and oral diseases. Update on the evidence, with recommendations|journal=Med Princ Pract|volume=12 Suppl 1|pages=22–32|year=2003|pmid=12707498|doi=10.1159/000069845}}</ref><ref>{{cite journal|author=Ness L, Rosekrans Dde L, Welford JF|title=An epidemiologic study of factors affecting extrinsic staining of teeth in an English population|journal=Community Dent Oral Epidemiol|volume=5|issue=1|pages=55–60|year=1977|month=January|pmid=264419}}</ref> [[Halitosis]] or bad breath is common among tobacco smokers<ref>{{Cite web |url=http://www.iwant2stopsmoking.com |title=Helping you to Stop Smoking! |accessdate=2008-01-04}}</ref>. Tooth loss has been shown to be 2<ref>{{cite journal|author=Albandar JM, Streckfus CF, Adesanya MR, Winn DM|title=Cigar, pipe, and cigarette smoking as risk factors for periodontal disease and tooth loss|journal=J. Periodontol.|volume=71|issue=12|pages=1874–81|year=2000|month=December|pmid=11156044}}</ref> to 3 times<ref>{{cite journal|author=Dietrich T, Maserejian NN, Joshipura KJ, Krall EA, Garcia RI|title=Tobacco use and incidence of tooth loss among US male health professionals|journal=J. Dent. Res.|volume=86|issue=4|pages=373–7|year=2007|month=April|pmid=17384035|url=http://jdr.iadrjournals.org/cgi/pmidlookup?view=long&pmid=17384035}}</ref> higher in smokers than in non-smokers.<ref>{{cite journal|author=Al-Bayaty FH, Wahid NA, Bulgiba AM|title=Tooth mortality in smokers and nonsmokers in a selected population in Sana'a, Yemen|journal=J. Periodont. Res.|volume=43|issue=1|pages=9–13|year=2008|month=February|pmid=18230101|doi=10.1111/j.1600-0765.2007.00988.x}}</ref> In addition, complications may further include [[leukoplakia]] the adherent white plaques or patches on the mucous membranes of the oral cavity, including the tongue, and a loss of taste sensation or [[saliva]]ry changes.{{Citation needed|date=February 2007}}
Perhaps the most serious oral condition that can arise is that of [[oral cancer]]. However, smoking also increases the risk for various other oral diseases, some almost completely exclusive to tobacco users. The [[National Institutes of Health]], through the [[National Cancer Institute]], determined in 1998 that "cigar smoking causes a variety of cancers including cancers of the [[oral cancer|oral cavity]] (lip, tongue, mouth, throat), [[Esophageal cancer|esophagus]], [[Laryngeal cancer|larynx]], and [[lung cancer|lung]]."<ref name=NIH>{{Cite web|url=http://www.nih.gov/news/pr/apr98/nci-10a.htm|title=Background on Cigar Monograph: Cigars: Health Effects and Trends|date=1998-04-10|accessdate=2008-01-04|author=[[National Institutes of Health]] }}</ref> [[Smoking pipe (tobacco)|Pipe]] smoking involves significant health risks,<ref>{{Cite web|url=http://jnci.oxfordjournals.org/cgi/content/full/96/11/853/T2|title=Questions About Smoking, Tobacco, and Health|author=[[American Cancer Society]]|accessdate=2008-01-04}}</ref><ref>{{Cite pmid|15173269}}</ref> particularly oral cancer.<ref>{{Cite web|url=http://www.ahealthyme.com/topic/pipes|author=Loren Stein|title=Pipe Smoking|publisher=A Healthy Me!|accessdate=2008-01-04}}</ref><ref>{{Cite web|url=http://books.nap.edu/openbook.php?record_id=943&page=250|author=Commission on Life Sciences|title=Environmental Tobacco Smoke: Measuring Exposures and Assessing Health Effects (1986)|accessdate=2008-01-04}}</ref> Roughly half of [[periodontitis]] or inflammation around the teeth cases attributed to current or former smoking. Smokeless tobacco causes [[gingival recession]] and white [[mucosal]] [[lesion]]s. Up to 90% of periodontitis patients who are not helped by common modes of treatment are smokers. Smokers have significantly greater loss of bone height than nonsmokers, and the trend can be extend to pipe smokers to have more bone loss than nonsmokers.<ref name="pmid11336116">{{Cite pmid|11336116}}</ref> Smoking has been proven to be an important factor in the staining of teeth.<ref name="pmid12707498">{{Cite doi|10.1159/000069845}}</ref><ref>{{Cite pmid|264419}}</ref> [[Halitosis]] or bad breath is common among tobacco smokers<ref>{{Cite web|url=http://www.iwant2stopsmoking.com|title=Helping you to Stop Smoking!|accessdate=2008-01-04}}</ref>. Tooth loss has been shown to be 2<ref>{{Cite pmid|1156044}}</ref> to 3 times<ref>{{Cite pmid|17384035}}</ref> higher in smokers than in non-smokers.<ref>{{Cite doi|10.1111/j.1600-0765.2007.00988.x}}</ref> In addition, complications may further include [[leukoplakia]] the adherent white plaques or patches on the mucous membranes of the oral cavity, including the tongue, and a loss of taste sensation or [[saliva]]ry changes.{{Citation needed|date=February 2007}}


===Infection===
===Infection===


Tobacco is also linked to susceptibility to infectious diseases, particularly in the lungs. Smoking more than 20 [[cigarette]]s a day increases the risk of [[tuberculosis]] by two to four times,<ref>{{cite journal|title=Smoking and tuberculosis: the epidemiological association and pathogenesis|author=Davies PDO, Yew WW, Ganguly D, ''et al.''|year=2006|volume=100|pages=291&ndash;8|journal=Trans R Soc Trop Med Hyg|pmid=16325875|doi=10.1016/j.trstmh.2005.06.034}}</ref><ref>{{cite journal|author=Jha P, Jacob B, Gajalakshmi V, ''et al.''|title=A nationally representative case–control study of smoking and death in India|journal=N Engl J Med|volume=358|pages=1137&ndash;1147|year=2008|issue=11|url=http://content.nejm.org/cgi/content/full/358/11/1137?query=TOC|doi=10.1056/NEJMsa0707719|pmid=18272886}}</ref> and being a current smoker has been linked to a fourfold increase in the risk of invasive pneumococcal disease.<ref>{{cite journal|title=Cigarette smoking and invasive pneumococcal disease.|author=Nuorti JP, Butler JC, Farley MM, ''et al.''|year=2000|volume=342|pages=681&ndash;9|journal=N Engl J Med|url=http://content.nejm.org/cgi/content/abstract/342/10/681|pmid=10706897|doi=10.1056/NEJM200003093421002}}</ref> It is believed that smoking increases the risk of these and other pulmonary and respiratory tract infections both through structural damage and through effects on the immune system. The effects on the immune system include an increase in CD4+ cell production attributable to nicotine, which has tentatively been linked to increased [[HIV]] susceptibility.<ref>{{cite journal|author=Arcavi L, Benowitz NL|title=Cigarette smoking and infection|year=2004|volume=164|pages=2206&ndash;16|url=http://archinte.ama-assn.org/cgi/content/full/164/20/2206|pmid=15534156|doi=10.1001/archinte.164.20.2206 }}</ref> The usage of tobacco also increases rates of infection: [[common cold]] and [[bronchitis]], [[chronic obstructive pulmonary disease]], [[emphysema]] and [[chronic bronchitis]] in particular.{{Citation needed|date=December 2008}}
Tobacco is also linked to susceptibility to infectious diseases, particularly in the lungs. Smoking more than 20 [[cigarette]]s a day increases the risk of [[tuberculosis]] by two to four times,<ref>{{Cite doi|10.1016/j.trstmh.2005.06.034}}</ref><ref>{{Cite doi|10.1056/NEJMsa0707719}}</ref> and being a current smoker has been linked to a fourfold increase in the risk of invasive pneumococcal disease.<ref>{{Cite doi|10.1056/NEJM200003093421002}}</ref> It is believed that smoking increases the risk of these and other pulmonary and respiratory tract infections both through structural damage and through effects on the immune system. The effects on the immune system include an increase in CD4+ cell production attributable to nicotine, which has tentatively been linked to increased [[HIV]] susceptibility.<ref>{{Cite doi|10.1001/archinte.164.20.2206 }}</ref> The usage of tobacco also increases rates of infection: [[common cold]] and [[bronchitis]], [[chronic obstructive pulmonary disease]], [[emphysema]] and [[chronic bronchitis]] in particular.{{Citation needed|date=December 2008}}


Smoking reduces the risk of [[Kaposi's sarcoma]] in people without [[HIV|HIV infection]].<ref>{{cite journal|author=Goedert JJ, Vitale F, Lauria C, ''et al.''|title=Risk factors for classical Kaposi's sarcoma|journal=J. Natl. Cancer Inst.|volume=94|issue=22|pages=1712–8|year=2002|month=November|pmid=12441327|url=http://jnci.oxfordjournals.org/cgi/pmidlookup?view=long&pmid=12441327}}</ref>
Smoking reduces the risk of [[Kaposi's sarcoma]] in people without [[HIV|HIV infection]].<ref>{{Cite pmid|12441327}}</ref>


===Impotence===
===Impotence===
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====Cognitive Function====
====Cognitive Function====
The usage of tobacco also creates cognitive dysfunction, which include: increased risk (or decrease)<ref name="alzheimer-almeida">{{cite journal|author=Osvaldo P. Almeida, Gary K. Hulse, David Lawrence, and Leon Flicker|year=2002|month=January|title=Smoking as a risk factor for Alzheimer's disease: contrasting evidence from a systematic review of case-control and cohort studies|journal=Addiction|volume=97|page=15|url=http://www.blackwell-synergy.com/links/doi/10.1046/j.1360-0443.2002.00016.x/full/|doi=10.1046/j.1360-0443.2002.00016.x }}</ref> of Alzheimer's disease and decline in cognitive abilities,<ref name="pmid17573335">{{cite journal|author=Anstey KJ, von Sanden C, Salim A, O'Kearney R|title=Smoking as a risk factor for dementia and cognitive decline: a meta-analysis of prospective studies|journal=Am. J. Epidemiol.|volume=166|issue=4|pages=367–78|year=2007|pmid=17573335|doi=10.1093/aje/kwm116}}</ref> reduced memory and cognitive abilities in adolescent smokers,<ref name="pmid15607301">{{cite journal|author=Jacobsen LK, Krystal JH, Mencl WE, Westerveld M, Frost SJ, Pugh KR|title=Effects of smoking and smoking abstinence on cognition in adolescent tobacco smokers|journal=Biol. Psychiatry|volume=57|issue=1|pages=56–66|year=2005|pmid=15607301|doi=10.1016/j.biopsych.2004.10.022}}</ref> brain shrinkage (cerebral atrophy)<ref>{{cite journal|author=Brody AL, Mandelkern MA, Jarvik ME, ''et al.''|title=Differences between smokers and nonsmokers in regional gray matter volumes and densities|journal=Biol. Psychiatry|volume=55|issue=1|pages=77–84|year=2004|month=January|pmid=14706428|url=http://linkinghub.elsevier.com/retrieve/pii/S0006322303006103}}</ref><ref>{{cite journal|author=Akiyama H, Meyer JS, Mortel KF, Terayama Y, Thornby JI, Konno S|title=Normal human aging: factors contributing to cerebral atrophy|journal=J. Neurol. Sci.|volume=152|issue=1|pages=39–49|year=1997|month=November|pmid=9395125|url=http://linkinghub.elsevier.com/retrieve/pii/S0022510X9700141X}}</ref>
The usage of tobacco also creates cognitive dysfunction, which include: increased risk (or decrease)<ref name="alzheimer-almeida">{{Cite doi|10.1046/j.1360-0443.2002.00016.x}}</ref> of Alzheimer's disease and decline in cognitive abilities,<ref name="pmid17573335">{{Cite doi|10.1093/aje/kwm116}}</ref> reduced memory and cognitive abilities in adolescent smokers,<ref name="pmid15607301">{{Cite doi|10.1016/j.biopsych.2004.10.022}}</ref> brain shrinkage (cerebral atrophy)<ref>{{Cite pmid|14706428}}</ref><ref>{{Cite pmid|9395125}}</ref>


In many respects, [[nicotine]] acts on the nervous system in a similar way to [[caffeine]]. Some writings have stated that smoking can also increase mental [[concentration]]; one study documents a significantly better performance on the normed Advanced Raven Progressive Matrices test after smoking.<ref>Con Stough, Gordon Mangan, Tim Bates, O. Pellett (1994) Smoking and Raven IQ. Psycho-pharmacology 116:382-384</ref>
In many respects, [[nicotine]] acts on the nervous system in a similar way to [[caffeine]]. Some writings have stated that smoking can also increase mental [[concentration]]; one study documents a significantly better performance on the normed Advanced Raven Progressive Matrices test after smoking.<ref>Con Stough, Gordon Mangan, Tim Bates, O. Pellett (1994) Smoking and Raven IQ. Psycho-pharmacology 116:382-384</ref>


Most smokers, when denied access to [[nicotine]], exhibit symptoms such as irritability, jitteriness, dry mouth, and rapid heart beat.<ref name="Why people smoke">{{cite journal|author=Jarvis MJ|title=Why people smoke|journal=BMJ|volume=328|issue=7434|pages=277–9|year=2004|month=January|pmid=14751901|pmc=324461|doi=10.1136/bmj.328.7434.277|url=http://www.bmj.com/cgi/reprint/328/7434/277}}</ref> The onset of these symptoms is very fast, nicotine's half-life being only 2 hours. Withdrawal symptoms can appear even if the smoker's consumption is very limited or irregular, appearing after only 4-5 cigarettes in most adolescents. An ex-smoker's chemical dependence to nicotine will cease after approximately ten to twenty days, although the brain's number of nicotine receptors is permanently altered,<ref>J Pharm Ecp Ther.1994 Oct;271(1)125-33 PMID 7965705</ref> and the [[psychological]] dependence may linger for months or even many years. Unlike some [[recreational drug use|recreational drugs]], nicotine does not measurably alter a smoker's [[motor skills]], [[judgement]], or [[language]] abilities while under the influence of the drug. Tobacco withdrawal has been shown to cause clinically significant distress.<ref>{{cite journal|author=Hughes JR|title=Clinical significance of tobacco withdrawal|journal=Nicotine Tob. Res.|volume=8|issue=2|pages=153–6|year=2006|month=April|pmid=16766409|doi=10.1080/14622200500494856}}</ref>
Most smokers, when denied access to [[nicotine]], exhibit symptoms such as irritability, jitteriness, dry mouth, and rapid heart beat.<ref name="Why people smoke">{{Cite doi|10.1136/bmj.328.7434.277}}</ref> The onset of these symptoms is very fast, nicotine's half-life being only 2 hours. Withdrawal symptoms can appear even if the smoker's consumption is very limited or irregular, appearing after only 4-5 cigarettes in most adolescents. An ex-smoker's chemical dependence to nicotine will cease after approximately ten to twenty days, although the brain's number of nicotine receptors is permanently altered,<ref>{{Cite pmid|7965705}}</ref> and the [[psychological]] dependence may linger for months or even many years. Unlike some [[recreational drug use|recreational drugs]], nicotine does not measurably alter a smoker's [[motor skills]], [[judgement]], or [[language]] abilities while under the influence of the drug. Tobacco withdrawal has been shown to cause clinically significant distress.<ref>{{Cite doi|10.1080/14622200500494856}}</ref>


Most notably, some studies have found that patients with [[Alzheimer's disease]] are more likely not to have smoked than the general population, which has been interpreted to suggest that smoking offers some protection against Alzheimer's. However, the research in this area is limited and the results are conflicting; some studies show that smoking increases the risk of Alzheimer's disease. A recent review of the available scientific literature concluded that the apparent decrease in Alzheimer risk may be simply due to the fact that smokers tend to die before reaching the age at which Alzheimer normally occurs. "Differential mortality is always likely to be a problem where there is a need to investigate the effects of smoking in a disorder with very low incidence rates before age 75 years, which is the case of Alzheimer's disease," it stated, noting that smokers are only half as likely as non-smokers to survive to the age of 80.<ref name="alzheimer-almeida" />
Most notably, some studies have found that patients with [[Alzheimer's disease]] are more likely not to have smoked than the general population, which has been interpreted to suggest that smoking offers some protection against Alzheimer's. However, the research in this area is limited and the results are conflicting; some studies show that smoking increases the risk of Alzheimer's disease. A recent review of the available scientific literature concluded that the apparent decrease in Alzheimer risk may be simply due to the fact that smokers tend to die before reaching the age at which Alzheimer normally occurs. "Differential mortality is always likely to be a problem where there is a need to investigate the effects of smoking in a disorder with very low incidence rates before age 75 years, which is the case of Alzheimer's disease," it stated, noting that smokers are only half as likely as non-smokers to survive to the age of 80.<ref name="alzheimer-almeida" />


Former and current smokers have a lower incidence of [[Parkinson's disease]] compared to people who have never smoked,<ref>{{cite journal|author=Allam MF, Campbell MJ, Hofman A, Del Castillo AS, Fernández-Crehuet Navajas R|title=Smoking and Parkinson's disease: systematic review of prospective studies|journal=Mov. Disord.|volume=19|issue=6|pages=614–21|year=2004|month=June|pmid=15197698|doi=10.1002/mds.20029}}</ref><ref>{{cite journal|author=Allam MF, Campbell MJ, Del Castillo AS, Fernández-Crehuet Navajas R|title=Parkinson's disease protects against smoking?|journal=Behav Neurol|volume=15|issue=3-4|pages=65–71|year=2004|pmid=15706049|url=http://iospress.metapress.com/openurl.asp?genre=article&issn=0953-4180&volume=15&issue=3&spage=65}}</ref> although the authors stated that it was more likely that the movement disorders which are part of Parkinson's disease prevented people from being able to smoke than that smoking itself was protective. Another study considered a possible role of nicotine in reducing Parkinson's risk: nicotine stimulates the [[dopaminergic]] system of the brain, which is damaged in Parkinson's disease, while other compounds in tobacco smoke inhibit [[MAO-B]], an enzyme which produces oxidative radicals by breaking down dopamine.<ref>{{Cite journal|issn=01662236|volume=27|issue=9|pages=561–8|last=Quik|first=Maryka|title=Smoking, nicotine and Parkinson's disease|journal=Trends in neurosciences|date=2004-09|pmid=15331239|doi=10.1016/j.tins.2004.06.008}}</ref>
Former and current smokers have a lower incidence of [[Parkinson's disease]] compared to people who have never smoked,<ref>{{Cite doi|10.1002/mds.20029}}</ref><ref>{{Cite pmid|15706049}}</ref> although the authors stated that it was more likely that the movement disorders which are part of Parkinson's disease prevented people from being able to smoke than that smoking itself was protective. Another study considered a possible role of nicotine in reducing Parkinson's risk: nicotine stimulates the [[dopaminergic]] system of the brain, which is damaged in Parkinson's disease, while other compounds in tobacco smoke inhibit [[MAO-B]], an enzyme which produces oxidative radicals by breaking down dopamine.<ref>{{Cite doi|10.1016/j.tins.2004.06.008}}</ref>


A very large percentage of [[Schizophrenia#Tobacco|schizophrenics]] smoke tobacco as a form of self medication.<ref name="mcneill">{{cite paper|author=McNeill, Ann|title=Smoking and mental health - a review of the literature|publisher=SmokeFree London Programme|year=2001|url=http://oldash.org.uk/html/policy/menlitrev.pdf|format=PDF|accessdate=2008-10-05 }}</ref><ref name="ocps">{{cite paper|author=Meltzer, H., Gill, B., Petticrew, M., Hinds. K.|title=OPCS Surveys of Psychiatric Morbidity Report 3: Economic Activity and Social Functioning of Adults With Psychiatric Disorders.|publisher=London, Her Majesty’s Stationery Office|year=1995}}</ref><ref name="kelly_mccreadie">{{cite journal|last=Kelly|first=Ciara|coauthors=McCreadie, Robin G.|title=Smoking Habits, Current Symptoms, and Premorbid Characteristics of Schizophrenic Patients in Nithsdale, Scotland|journal=[[American Journal of Psychiatry|The American Journal of Psychiatry]]|volume=156|pages=1751–7|publisher=[[American Psychiatric Association]]|date=1 November 1999|url=http://ajp.psychiatryonline.org/cgi/content/abstract/156/11/1751|accessdate=2006-12-14|pmid=10553739|issue=11}}</ref><ref name="hughes_et_al">{{cite journal|last=Hughes|first=J.R.|coauthors=Hatsukami, D.K., Mitchell, J.E., & Dahlgren, L.A.|title=Prevalence of smoking among psychiatric outpatients|journal=[[American Journal of Psychiatry|The American Journal of Psychiatry]]|volume=143|pages=993–7|publisher=[[American Psychiatric Association]]|date=1 August 1986|url=http://ajp.psychiatryonline.org/cgi/content/abstract/143/8/993|accessdate=2006-12-14|pmid=3487983|issue=8}}</ref> The high rate of tobacco use by the mentally ill is a major factor in their decreased life expectancy, which is about 25 years shorter than the general population.<ref>{{cite journal|author=Schroeder SA|title=Shattuck Lecture. We can do better--improving the health of the American people|journal=N. Engl. J. Med.|volume=357|issue=12|pages=1221–8|year=2007|pmid=17881753|doi=10.1056/NEJMsa073350}}</ref> Following the observation that smoking improves condition of people with schizophrenia, in particular working memory deficit, [[nicotine patch]]es had been proposed as a way to treat schizophrenia.<ref>[http://www.abc.net.au/rn/healthreport/stories/2002/614060.htm Health Report - 22 July 2002 - Schizophrenia and Smoking<!-- Bot generated title -->]</ref> Some studies suggest that a link exists between smoking and mental illness, citing the high incidence of smoking amongst those suffering from [[schizophrenia]]<ref>{{cite journal|author=Sacco KA, Bannon KL, George TP|title=Nicotinic receptor mechanisms and cognition in normal states and neuropsychiatric disorders|journal=J. Psychopharmacol. (Oxford)|volume=18|issue=4|pages=457–74|year=2004|month=December|pmid=15582913|pmc=1201375|doi=10.1177/0269881104047273}}</ref> and the possibility that smoking may alleviate some of the symptoms of mental illness,<ref>{{cite journal|author=Kumari V, Postma P|title=Nicotine use in schizophrenia: the self medication hypotheses|journal=Neurosci Biobehav Rev|volume=29|issue=6|pages=1021–34|year=2005|pmid=15964073|doi=10.1016/j.neubiorev.2005.02.006}}</ref> but these have not been conclusive.
A very large percentage of [[Schizophrenia#Tobacco|schizophrenics]] smoke tobacco as a form of self medication.<ref name="mcneill">{{Cite paper|author=McNeill, Ann|title=Smoking and mental health - a review of the literature|publisher=SmokeFree London Programme|year=2001|url=http://oldash.org.uk/html/policy/menlitrev.pdf|format=PDF|accessdate=2008-10-05 }}</ref><ref name="ocps">{{Cite paper|author=Meltzer, H., Gill, B., Petticrew, M., Hinds. K.|title=OPCS Surveys of Psychiatric Morbidity Report 3: Economic Activity and Social Functioning of Adults With Psychiatric Disorders.|publisher=London, Her Majesty’s Stationery Office|year=1995}}</ref><ref name="kelly_mccreadie">{{Cite pmid|10553739}}</ref><ref name="hughes_et_al">{{Cite pmid|3487983}}</ref> The high rate of tobacco use by the mentally ill is a major factor in their decreased life expectancy, which is about 25 years shorter than the general population.<ref>{{Cite doi|10.1056/NEJMsa073350}}</ref> Following the observation that smoking improves condition of people with schizophrenia, in particular working memory deficit, [[nicotine patch]]es had been proposed as a way to treat schizophrenia.<ref>[http://www.abc.net.au/rn/healthreport/stories/2002/614060.htm Health Report - 22 July 2002 - Schizophrenia and Smoking<!-- Bot generated title -->]</ref> Some studies suggest that a link exists between smoking and mental illness, citing the high incidence of smoking amongst those suffering from [[schizophrenia]]<ref>{{Cite doi|10.1177/0269881104047273}}</ref> and the possibility that smoking may alleviate some of the symptoms of mental illness,<ref>{{Cite doi|10.1016/j.neubiorev.2005.02.006}}</ref> but these have not been conclusive.


Recent studies have linked smoking to anxiety disorders, suggesting the correlation (and possibly mechanism) may be related to the broad class of anxiety disorders, and not limited to just depression. Current ongoing research are attempting to explore the addiction-anxiety relationship.
Recent studies have linked smoking to anxiety disorders, suggesting the correlation (and possibly mechanism) may be related to the broad class of anxiety disorders, and not limited to just depression. Current ongoing research are attempting to explore the addiction-anxiety relationship.


Data from multiple studies suggest that anxiety disorders and depression play a role in cigarette smoking.<ref>[http://jama.ama-assn.org/cgi/content/abstract/264/12/1541 Depression and the dynamics of smoking. A national perspective]</ref>
Data from multiple studies suggest that anxiety disorders and depression play a role in cigarette smoking.<ref>[http://jama.ama-assn.org/cgi/content/abstract/264/12/1541 Depression and the dynamics of smoking. A national perspective]</ref>
A history of regular smoking was observed more frequently among individuals who had experienced a [[major depressive disorder]] at some time in their lives than among individuals who had never experienced major depression or among individuals with no psychiatric diagnosis.<ref>[http://jama.ama-assn.org/cgi/content/abstract/264/12/1546 Smoking, smoking cessation, and major depression]</ref> People with major depression are also much less likely to [[smoking cessation|quit]] due to the increased risk of experiencing mild to severe states of depression, including a major depressive episode.<ref>{{cite journal|author=Covey LS, Glassman AH, Stetner F|title=Cigarette smoking and major depression|journal=J Addict Dis|volume=17|issue=1|pages=35–46|year=1998|pmid=9549601|doi=10.1300/J069v17n01_04 }}</ref> Depressed smokers appear to experience more withdrawal symptoms on quitting, are less likely to be successful at quitting, and are more likely to relapse.<ref>{{cite journal|author=Hall SM, Muñoz RF, Reus VI, Sees KL|title=Nicotine, negative affect, and depression|journal=J Consult Clin Psychol|volume=61|issue=5|pages=761–7|year=1993|month=October|pmid=7902368|url=http://content.apa.org/journals/ccp/61/5/761|doi=10.1037/0022-006X.61.5.761}}</ref>
A history of regular smoking was observed more frequently among individuals who had experienced a [[major depressive disorder]] at some time in their lives than among individuals who had never experienced major depression or among individuals with no psychiatric diagnosis.<ref>[http://jama.ama-assn.org/cgi/content/abstract/264/12/1546 Smoking, smoking cessation, and major depression]</ref> People with major depression are also much less likely to [[smoking cessation|quit]] due to the increased risk of experiencing mild to severe states of depression, including a major depressive episode.<ref>{{Cite doi|10.1300/J069v17n01_04 }}</ref> Depressed smokers appear to experience more withdrawal symptoms on quitting, are less likely to be successful at quitting, and are more likely to relapse.<ref>{{Cite doi|10.1037/0022-006X.61.5.761}}</ref>


Evidence suggests that non-smokers are up to twice as likely as smokers to develop [[Parkinson's disease]] or [[Alzheimer's disease]].<ref>{{Cite doi|10.1016/S0166-4328(00)00206-0}}</ref> A plausible explanation for these cases may be the effect of nicotine, a [[cholinergic]] [[stimulant]], decreasing the levels of [[acetylcholine]] in the smoker's brain; Parkinson's disease occurs when the effect of [[dopamine]] is less than that of acetylcholine. In addition, nicotine stimulates the mesolimbic dopamine pathway (as do other drugs of abuse), causing an effective increase in dopamine levels. Opponents counter by noting that consumption of pure nicotine may be as beneficial as smoking without the risks associated with smoking, although this is unlikely due to the importance of the MAO-B inhibitor compounds of tobacco in preventing neurodegenerative diseases.
Evidence suggests that non-smokers are up to twice as likely as smokers to develop [[Parkinson's disease]] or [[Alzheimer's disease]].<ref>{{cite journal
|author=Fratiglioni L, Wang HX
|title=Smoking and Parkinson's and Alzheimer's disease: review of the epidemiological studies
|journal=Behav Brain Res
|volume=113
|issue=1–2
|pages=117–120
|month=August|year=2000
|pmid=10942038
|doi=10.1016/S0166-4328(00)00206-0
}}</ref>
A plausible explanation for these cases may be the effect of nicotine, a [[cholinergic]] [[stimulant]], decreasing the levels of [[acetylcholine]] in the smoker's brain; Parkinson's disease occurs when the effect of [[dopamine]] is less than that of acetylcholine. In addition, nicotine stimulates the mesolimbic dopamine pathway (as do other drugs of abuse), causing an effective increase in dopamine levels. Opponents counter by noting that consumption of pure nicotine may be as beneficial as smoking without the risks associated with smoking, although this is unlikely due to the importance of the MAO-B inhibitor compounds of tobacco in preventing neurodegenerative diseases.


===In pregnancy===
===In pregnancy===
{{See|Effects of smoking during pregnancy}}
{{See|Effects of smoking during pregnancy}}
A number of studies have shown that tobacco use is a significant factor in [[miscarriage]]s among [[pregnant]] smokers, and that it contributes to a number of other threats to the health of the fetus.<ref name=pmid9929522>{{cite journal|author=Ness RB, Grisso JA, Hirschinger N, ''et al.''|title=Cocaine and tobacco use and the risk of spontaneous abortion|journal=N. Engl. J. Med. |volume=340 |issue=5 |pages=333–9 |year=1999 |month=February |pmid=9929522 |url=http://content.nejm.org/cgi/pmidlookup?view=short&pmid=9929522&promo=ONFLNS19}}</ref><ref name=pmid11978283>{{cite journal|author=Oncken C, Kranzler H, O'Malley P, Gendreau P, Campbell WA|title=The effect of cigarette smoking on fetal heart rate characteristics|journal=Obstet Gynecol |volume=99 |issue=5 Pt 1 |pages=751–5 |year=2002 |month=May |pmid=11978283 |url=http://www.greenjournal.org/cgi/pmidlookup?view=long&pmid=11978283}}</ref> Second-hand smoke appears to present an equal danger to the fetus, as one study noted that "heavy ''paternal'' smoking increased the risk of early pregnancy loss."<ref name="t">{{cite journal|author=Venners SA, Wang X, Chen C, ''et al.''|title=Paternal smoking and pregnancy loss: a prospective study using a biomarker of pregnancy|journal=Am. J. Epidemiol.|volume=159|issue=10|pages=993–1001|year=2004|month=May|pmid=15128612|url=http://aje.oxfordjournals.org/cgi/pmidlookup?view=long&pmid=15128612}}</ref>
A number of studies have shown that tobacco use is a significant factor in [[miscarriage]]s among [[pregnant]] smokers, and that it contributes to a number of other threats to the health of the fetus.<ref name=pmid9929522>{{Cite pmid|9929522}}</ref><ref name=pmid11978283>{{Cite pmid|11978283}}</ref> Second-hand smoke appears to present an equal danger to the fetus, as one study noted that "heavy ''paternal'' smoking increased the risk of early pregnancy loss."<ref name="t">{{Cite pmid|15128612}}</ref>


===Other===
===Other===


Studies suggest that smoking decreases appetite, but did not conclude that overweight people should smoke or that their health would improve by smoking.<ref>News-Medical.Net, [http://www.news-medical.net/?id=5991], accessed on Jan 3, 2008</ref><ref>mytelus.com, [http://health.mytelus.com/channel_section_details.asp?text_id=3622&channel_id=1055&relation_id=30136&article_rating=1], accessed on Jan 3, 2008</ref> Smoking also decreases weight by overexpressing the gene [[AZGP1]] which stimulates [[lipolysis]].<ref name=smoking>{{cite journal|title=Cigarette Smoking Induces Overexpression of a Fat-Depleting Gene AZGP1 in the Human.|journal=Chest|volume=135|issue=5|pages=1197–208|year=2009|pmid=19188554}}</ref>
Studies suggest that smoking decreases appetite, but did not conclude that overweight people should smoke or that their health would improve by smoking.<ref>News-Medical.Net, [http://www.news-medical.net/?id=5991], accessed on Jan 3, 2008</ref><ref>mytelus.com, [http://health.mytelus.com/channel_section_details.asp?text_id=3622&channel_id=1055&relation_id=30136&article_rating=1], accessed on Jan 3, 2008</ref> Smoking also decreases weight by overexpressing the gene [[AZGP1]] which stimulates [[lipolysis]].<ref name=smoking>{{Cite pmid|19188554}}</ref>


Preliminary reports suggest that smoking can decrease the incidence of [[acne]] [[prophylactic]]ally. This was seen by a decreased percentage ratio of patients needing acne medication versus the percentage of entire population of smokers. (A smaller percentage of patients who smoked needed medication than found in the population as a whole).<ref>{{cite journal|author=Alireza Firooz, Reza Sarhangnejad, Seyyed Massoud Davoudi, and Mansour Nassiri-Kashani|title=Acne and Smoking, Is There a relationship?|journal=BMC Dermatology|volume=5|page=2|year=2005|doi=10.1186/1471-5945-5-2}}</ref>
Preliminary reports suggest that smoking can decrease the incidence of [[acne]] [[prophylactic]]ally. This was seen by a decreased percentage ratio of patients needing acne medication versus the percentage of entire population of smokers. (A smaller percentage of patients who smoked needed medication than found in the population as a whole).<ref>{{Cite doi|10.1186/1471-5945-5-2}}</ref>


A protective effect of current smoking against [[ulcerative colitis]], although smoking ''increases'' the risk of [[Crohn's disease]], the other form of [[inflammatory bowel disease]].<ref>{{cite journal|author=Mahid SS, Minor KS, Soto RE, Hornung CA, Galandiuk S|title=Smoking and inflammatory bowel disease: a meta-analysis|journal=Mayo Clin. Proc.|volume=81|issue=11|pages=1462–71|year=2006|month=November|pmid=17120402}}</ref> There is some evidence for decreased rates of [[endometriosis]] in infertile smoking women,<ref>{{cite journal|author=Missmer SA, Hankinson SE, Spiegelman D, Barbieri RL, Marshall LM, Hunter DJ|title=Incidence of laparoscopically confirmed endometriosis by demographic, anthropometric, and lifestyle factors|journal=Am. J. Epidemiol.|volume=160|issue=8|pages=784–96|year=2004|month=October|pmid=15466501|doi=10.1093/aje/kwh275}}</ref> although other studies have found that smoking increases the risk in infertile women.<ref>{{cite journal|author=Calhaz-Jorge C, Mol BW, Nunes J, Costa AP|title=Clinical predictive factors for endometriosis in a Portuguese infertile population|journal=Hum. Reprod.|volume=19|issue=9|pages=2126–31|year=2004|month=September|pmid=15229202|doi=10.1093/humrep/deh374}}</ref> There is little or no evidence of a protective effect in fertile women. Some preliminary data from 1996 suggested a reduced incidence of [[uterine fibroids]],<ref>{{cite journal|author=Baron JA|title=Beneficial effects of nicotine and cigarette smoking: the real, the possible and the spurious|journal=Br. Med. Bull.|volume=52|issue=1|pages=58–73|year=1996|month=January|pmid=8746297|url=http://bmb.oxfordjournals.org/cgi/pmidlookup?view=long&pmid=8746297}}</ref> but overall the evidence is unconvincing.<ref>{{cite journal|author=Schwartz SM, Marshall LM, Baird DD|title=Epidemiologic contributions to understanding the etiology of uterine leiomyomata|journal=Environ. Health Perspect.|volume=108 Suppl 5|pages=821–7|year=2000|month=October|pmid=11035989}}</ref>
A protective effect of current smoking against [[ulcerative colitis]], although smoking ''increases'' the risk of [[Crohn's disease]], the other form of [[inflammatory bowel disease]].<ref>{{Cite pmid|17120402}}</ref> There is some evidence for decreased rates of [[endometriosis]] in infertile smoking women,<ref>{{Cite doi|10.1093/aje/kwh275}}</ref> although other studies have found that smoking increases the risk in infertile women.<ref>{{Cite doi|10.1093/humrep/deh374}}</ref> There is little or no evidence of a protective effect in fertile women. Some preliminary data from 1996 suggested a reduced incidence of [[uterine fibroids]],<ref>{{Cite pmid|8746297}}</ref> but overall the evidence is unconvincing.<ref>{{Cite pmid|11035989}}</ref>


A new research has found that women who smoke are at significantly increased risk of developing an abdominal [[aortic]] [[aneurysm]], a condition in which a weak area of the [[abdominal]] aorta expands or bulges.<ref>[http://www.themedguru.com/articles/smoking_may_perk_up_womens_risk_of_developing_deadly_aaa-86114529.html Smoking may perk up women's risk of developing deadly AAA | TheMedGuru<!-- Bot generated title -->]</ref>
A new research has found that women who smoke are at significantly increased risk of developing an abdominal [[aortic]] [[aneurysm]], a condition in which a weak area of the [[abdominal]] aorta expands or bulges.<ref>[http://www.themedguru.com/articles/smoking_may_perk_up_womens_risk_of_developing_deadly_aaa-86114529.html Smoking may perk up women's risk of developing deadly AAA|TheMedGuru<!-- Bot generated title -->]</ref>


Several types of "Smoker’s Paradoxes",<ref name="cohen">{{Cite doi|10.1161/hc3201.094225}}</ref> (cases where smoking appears to have specific beneficial effects), have been observed; often the actual mechanism remains undetermined. Risk of [[ulcerative colitis]] has been frequently shown to be reduced by smokers on a dose-dependent basis; the effect is eliminated if the individual stops smoking.<ref name="ohcm">Longmore, M., Wilkinson, I., Torok, E. Oxford Handbook of Clinical Medicine (Fifth Edition) p. 232</ref><ref>{{Cite doi|10.1046/j.1365-2036.2000.00847.x}}</ref> Smoking appears to interfere with development of [[Kaposi's sarcoma]],<ref>{{Cite news|title=Smoking Cuts Risk of Rare Cancer|publisher=UPI|date=March 29, 2001|url=http://www.data-yard.net/10b/kaposi.htm}}</ref> [[breast cancer]] among women carrying the very high risk [[BRCA]] gene,<ref>{{Cite news|author=Recer Paul|title=Cigarettes May Have an Up Side|agency=Associated Press|date=May 19, 1998|url=http://www.forces.org/evidence/files/brea.htm|accessdate=November 6, 2006}}</ref> [[preeclampsia]],<ref>{{Cite pmid|11422156}}</ref> and [[atopy|atopic disorder]]s such as [[allergic asthma]].<ref>{{Cite doi|10.1046/j.1365-2222.2001.01096.x}}</ref>
Several types of "Smoker’s Paradoxes",<ref name="cohen">
A plausible mechanism of action in these cases may be the [[nicotine]] in tobacco smoke acting as an [[Inflammation|anti-inflammatory agent]] and interfering with the disease process.<ref name="sciam">{{Cite journal|author=Melton Lisa|title=Body Blazes|journal=Scientific American|month=June|year=2006|page=24|url=http://www.sciam.com/article.cfm?chanID=sa006&colID=5&articleID=00080902-A2CF-146C-9D1E83414B7F0000}}</ref>
{{cite journal
|last=Cohen
|first=David J
|authorlink=
|coauthors=Michel Doucet, Donald E. Cutlip, Kalon K.L. Ho, Jeffrey J. Popma, Richard E. Kuntz
|title=Impact of Smoking on Clinical and Angiographic Restenosis After Percutaneous Coronary Intervention
|journal=Circulation
|volume=104
|issue=
|page=773
|year=2001
|url=http://www.data-yard.net/34/circulation_2001_104_773.htm
|doi=10.1161/hc3201.094225
|pmid=11502701
}}
</ref> (cases where smoking appears to have specific beneficial effects), have been observed; often the actual mechanism remains undetermined. Risk of [[ulcerative colitis]] has been frequently shown to be reduced by smokers on a dose-dependent basis; the effect is eliminated if the individual stops smoking.<ref name="ohcm">Longmore, M., Wilkinson, I., Torok, E. Oxford Handbook of Clinical Medicine (Fifth Edition) p. 232</ref><ref>{{cite journal
|author=Green JT, Richardson C, Marshall RW, Rhodes J, McKirdy HC, Thomas GA, Williams GT
|title=Nitric oxide mediates a therapeutic effect of nicotine in ulcerative colitis
|journal=Aliment Pharmacol Ther
|volume=14
|issue=11
|pages=1429–1434
|date=2000-11
|pmid=11069313
|doi=10.1046/j.1365-2036.2000.00847.x
}}</ref>
Smoking appears to interfere with development of [[Kaposi's sarcoma]],<ref>{{cite news
|last=
|first=
|coauthors=
|title=Smoking Cuts Risk of Rare Cancer
|work=
|pages=
|publisher=UPI
|date=March 29, 2001
|url=http://www.data-yard.net/10b/kaposi.htm
}}</ref>
[[breast cancer]] among women carrying the very high risk [[BRCA]] gene,<ref>{{cite news
|author=Recer Paul
|title=Cigarettes May Have an Up Side
|work=
|pages=
|agency=Associated Press
|date=May 19, 1998
|url=http://www.forces.org/evidence/files/brea.htm
|accessdate=November 6, 2006}}
</ref>
[[preeclampsia]],<ref>{{cite journal
|author=Lain Kristine Y, Powers Robert W, Krohn Marijane A, Ness Roberta B, Crombleholme William R, Roberts James M
|title=Urinary cotinine concentration confirms the reduced risk of preeclampsia with tobacco exposure
|journal=American Journal of Obstetrics and Gynecology
|volume=181
|issue=5
|pages=908–914
|month=November|year=1991
|url=http://www.data-yard.net/2/13/ajog.htm
|pmid=11422156
}}
</ref>
and [[atopy|atopic disorder]]s such as [[allergic asthma]].<ref>{{cite journal
|author=Hjern A, Hedberg A, Haglund B, Rosen M
|title=Does tobacco smoke prevent atopic disorders? A study of two generations of Swedish residents
|journal=Clin Exp Allergy
|volume=31
|issue=6
|pages=908–914
|publisher=
|month=June|year=2001
|url=http://www.data-yard.net/30/asthma.htm
|pmid=11422156
|doi=10.1046/j.1365-2222.2001.01096.x
}}</ref>
A plausible mechanism of action in these cases may be the [[nicotine]] in tobacco smoke acting as an [[Inflammation|anti-inflammatory agent]] and interfering with the disease process.<ref name="sciam">{{cite journal|author=Melton Lisa|title=Body Blazes|journal=Scientific American|month=June|year=2006|page=24|url=http://www.sciam.com/article.cfm?chanID=sa006&colID=5&articleID=00080902-A2CF-146C-9D1E83414B7F0000}}</ref>


==History==
==History==
Line 322: Line 224:
The late-19th century invention of automated cigarette-making machinery in the American South made possible mass production of cigarettes at low cost, and cigarettes became elegant and fashionable among society men as the Victorian era gave way to the Edwardian. In 1912, American Dr. Isaac Adler was the first to strongly suggest that lung [[cancer]] is related to smoking.<ref>Isaac Adler. "Primary Malignant Growth of the Lung and Bronchi". (1912) New York, Longmans, Green. pp. 3-12. [http://caonline.amcancersoc.org/cgi/reprint/30/5/295.pdf Reprinted (1980)] by ''A Cancer Journal for Clinicians''</ref> In 1929, Fritz Lickint of [[Dresden]], [[Germany]], published a formal statistical evidence of a lung cancer–tobacco link, based on a study showing that [[lung cancer]] sufferers were likely to be smokers.<ref name=about_lickint>[http://ije.oxfordjournals.org/cgi/content/full/30/1/31 Commentary: Schairer and Schoniger's forgotten tobacco epidemiology and the Nazi quest for racial purity - Proctor 30 (1): 31 - International Journal of Epidemiology]</ref> Lickint also argued that tobacco use was the best way to explain the fact that lung cancer struck men four or five times more often than women (since women smoked much less).<ref name=about_lickint />
The late-19th century invention of automated cigarette-making machinery in the American South made possible mass production of cigarettes at low cost, and cigarettes became elegant and fashionable among society men as the Victorian era gave way to the Edwardian. In 1912, American Dr. Isaac Adler was the first to strongly suggest that lung [[cancer]] is related to smoking.<ref>Isaac Adler. "Primary Malignant Growth of the Lung and Bronchi". (1912) New York, Longmans, Green. pp. 3-12. [http://caonline.amcancersoc.org/cgi/reprint/30/5/295.pdf Reprinted (1980)] by ''A Cancer Journal for Clinicians''</ref> In 1929, Fritz Lickint of [[Dresden]], [[Germany]], published a formal statistical evidence of a lung cancer–tobacco link, based on a study showing that [[lung cancer]] sufferers were likely to be smokers.<ref name=about_lickint>[http://ije.oxfordjournals.org/cgi/content/full/30/1/31 Commentary: Schairer and Schoniger's forgotten tobacco epidemiology and the Nazi quest for racial purity - Proctor 30 (1): 31 - International Journal of Epidemiology]</ref> Lickint also argued that tobacco use was the best way to explain the fact that lung cancer struck men four or five times more often than women (since women smoked much less).<ref name=about_lickint />


Prior to World War I, lung cancer was considered to be a rare disease, which most physicians would never see during their career.<ref>{{cite journal|author=Witschi|title=A Short History of Lung Cancer|journal=Toxicol Sci|month=November|year=2001|volume=64|issue=1|pages=4–6|pmid=11606795}}</ref><ref>Adler I. Primary malignant growths of the lungs and bronchi. New York: Longmans, Green; 1912., cited in {{cite journal|author=Spiro SG, Silvestri GA|title=One hundred years of lung cancer.|journal=Am J Respir Crit Care Med|date=September 1, 2005|volume=172|issue=5|pages=523–529|pmid=15961694|doi=10.1164/rccm.200504-531OE}}</ref> With the postwar rise in popularity of cigarette smoking, however, came an epidemic of lung cancer.
Prior to World War I, lung cancer was considered to be a rare disease, which most physicians would never see during their career.<ref>{{Cite pmid|11606795}}</ref><ref>Adler I. Primary malignant growths of the lungs and bronchi. New York: Longmans, Green; 1912., cited in {{Cite doi|10.1164/rccm.200504-531OE}}</ref> With the postwar rise in popularity of cigarette smoking, however, came an epidemic of lung cancer.


In 1950, [[Richard Doll]] published research in the [[British Medical Journal]] showing a close link between smoking and lung cancer.<ref> {{cite journal|last=Doll|first=Rich|coauthors=and Hilly, A. Bradford|date=September 30, 1950|title=Smoking and carcinoma of the lung. Preliminary report|journal=British Medical Journal|volume=2|issue=4682|pages=739–48|pmid=14772469}}</ref> Four years later, in 1954 the [[British Doctors Study]], a study of some 40 thousand doctors over 20 years, confirmed the suggestion, based on which the government issued advice that smoking and lung cancer rates were related.<ref> {{cite journal|author=Doll Richard, Bradford Hilly A|date=June 26, 1954|title=The mortality of doctors in relation to their smoking habits. A preliminary report|journal=British Medical Journal|issue=4877|pages=1451–55|pmid=13160495|url=http://bmj.bmjjournals.com/cgi/reprint/328/7455/1529|doi=10.1136/bmj.328.7455.1529|volume=328}}</ref> The British Doctors Study lasted till 2001, with results published every ten years and final results published in 2004 by Doll and [[Richard Peto]].<ref name="Doll2004">{{cite journal|author=Doll R, Peto R, Boreham J, Sutherland I|title=Mortality in relation to smoking: 50 years' observation on male British doctors.|year=2004|pmid=15213107}}</ref> Much early research was also done by [[Alton Ochsner]]. [[Reader's Digest]] magazine for many years published frequent anti-smoking articles. In 1964 the United States [[Surgeon General of the United States|Surgeon General]]'s Report on Smoking and Health (referenced below), led millions of American smokers to quit, the banning of certain advertising, and the requirement of warning labels on tobacco products.
In 1950, [[Richard Doll]] published research in the [[British Medical Journal]] showing a close link between smoking and lung cancer.<ref>{{Cite pmid|14772469}}</ref> Four years later, in 1954 the [[British Doctors Study]], a study of some 40 thousand doctors over 20 years, confirmed the suggestion, based on which the government issued advice that smoking and lung cancer rates were related.<ref>{{Cite doi|10.1136/bmj.328.7455.1529|volume=328}}</ref> The British Doctors Study lasted till 2001, with results published every ten years and final results published in 2004 by Doll and [[Richard Peto]].<ref name="Doll2004">{{Cite pmid|15213107}}</ref> Much early research was also done by [[Alton Ochsner]]. [[Reader's Digest]] magazine for many years published frequent anti-smoking articles. In 1964 the United States [[Surgeon General of the United States|Surgeon General]]'s Report on Smoking and Health (referenced below), led millions of American smokers to quit, the banning of certain advertising, and the requirement of warning labels on tobacco products.


The Canadian province of [[British Columbia]] has the [[Tobacco Damages and Health Care Costs Recovery Act]].
The Canadian province of [[British Columbia]] has the [[Tobacco Damages and Health Care Costs Recovery Act]].


==References==
==References==
===Notes===


{{Reflist|colwidth=30em}}
{{Reflist|colwidth=30em}}


===Bibliography===
==Bibliography==


{{Sisterlinks|Tobacco}}
{{Sisterlinks|Tobacco}}


{{Refbegin}}
{{Refbegin}}
* <cite id="WHO2008MPOWER">{{cite web|url=http://www.who.int/entity/tobacco/mpower/mpower_report_full_2008.pdf|format=PDF|title=WHO REPORT on the global TOBACCO epidemic|accessdate=2008-01-01|year=2008|publisher=World Health Organization}}</cite>
* <cite id="WHO2008MPOWER">{{Cite web|url=http://www.who.int/entity/tobacco/mpower/mpower_report_full_2008.pdf|format=PDF|title=WHO REPORT on the global TOBACCO epidemic|accessdate=2008-01-01|year=2008|publisher=World Health Organization}}</cite>
* <cite id="WHO2004GBD">{{cite web|url=http://www.who.int/entity/healthinfo/global_burden_disease/GBD_report_2004update_full.pdf|format=PDF|title=The Global Burden of Disease 2004 Update|accessdate=2008-01-01|year=2008|publisher=World Health Organization}}</cite>
* <cite id="WHO2004GBD">{{Cite web|url=http://www.who.int/entity/healthinfo/global_burden_disease/GBD_report_2004update_full.pdf|format=PDF|title=The Global Burden of Disease 2004 Update|accessdate=2008-01-01|year=2008|publisher=World Health Organization}}</cite>
* {{citation|title=2004 Surgeon General's Report—The Health Consequences of Smoking|url=http://www.cdc.gov/tobacco/data_statistics/sgr/sgr_2004/chapters.htm|format=PDF|accessdate=2009-05-24|year=2004|publisher=Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health|location=Washington DC|chapter=Chapter 1: Introduction and Approach to Causal Inference|chapterurl=http://www.cdc.gov/tobacco/data_statistics/sgr/sgr_2004/00_pdfs/chapter1.pdf|ref=CITEREF_2004SurgeonGeneral_Chapter1}}
* {{citation|title=2004 Surgeon General's Report—The Health Consequences of Smoking|url=http://www.cdc.gov/tobacco/data_statistics/sgr/sgr_2004/chapters.htm|format=PDF|accessdate=2009-05-24|year=2004|publisher=Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health|location=Washington DC|chapter=Chapter 1: Introduction and Approach to Causal Inference|chapterurl=http://www.cdc.gov/tobacco/data_statistics/sgr/sgr_2004/00_pdfs/chapter1.pdf|ref=CITEREF_2004SurgeonGeneral_Chapter1}}
* <cite id="SurgeonGeneralPassiveSmoking2006">{{cite web|url=http://www.surgeongeneral.gov/library/secondhandsmoke/report/fullreport.pdf|title=The health consequences of involuntary exposure to tobacco smoke: a report of the Surgeon General|accessdate=2009-02-15|year=2006|format=PDF|publisher=U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health|location=Atlanta, U.S.}}</cite>
* <cite id="SurgeonGeneralPassiveSmoking2006">{{Cite web|url=http://www.surgeongeneral.gov/library/secondhandsmoke/report/fullreport.pdf|title=The health consequences of involuntary exposure to tobacco smoke: a report of the Surgeon General|accessdate=2009-02-15|year=2006|format=PDF|publisher=U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health|location=Atlanta, U.S.}}</cite>
* <cite id="ACS2004">{{Cite web|url=http://tobaccodocuments.org/pm/2073777259-7269.html|title=Cancer Facts and Figures 2004: Basic Cancer Facts|accessdate=2009-01-21|publisher=American Cancer Society}}</cite>
* <cite id="ACS2004">{{cite web
* <cite id="Lichtenstein2000">{{Cite book|coauthors=Paul Lichtenstein, Ph.D., Niels V. Holm, M.D., Ph.D., Pia K. Verkasalo, M.D., Ph.D., Anastasia Iliadou, M.Sc., Jaakko Kaprio, M.D., Ph.D., Markku Koskenvuo, M.D., Ph.D., Eero Pukkala, Ph.D., Axel Skytthe, M.Sc., and Kari Hemminki, M.D., Ph.D.|title=Environmental and Heritable Factors in the Causation of Cancer — Analyses of Cohorts of Twins from Sweden, Denmark, and Finland|url=http://content.nejm.org/cgi/content/full/343/2/78|accessdate=2009-01-21|volume=343|year=2000|publisher=New England Journal of Medicine}}</cite>
|url=http://tobaccodocuments.org/pm/2073777259-7269.html
* <cite id="Montesano2001">{{Cite web|url=http://www.journals.elsevierhealth.com/periodicals/ejc/article/PIIS0959804901002660/abstract|title=Environmental causes of human cancers|accessdate=2009-01-21|author=Montesano, R., and Hall, J.|year=2001|publisher=European Journal of Cancer}}</cite>
|title=Cancer Facts and Figures 2004: Basic Cancer Facts
|accessdate=2009-01-21
|author=
|last=
|first=
|authorlink=
|coauthors=
|date=
|year=
|month=
|work=
|publisher=American Cancer Society
|location=
|pages=
|language=
|doi=
|archiveurl=
|archivedate=
|quote=
}}</cite><!-- ACS. 2004. Cancer Facts and Figures 2004: Basic Cancer Facts. American Cancer Society. [http://cancer.org/statistics/cff99/basicfacts.html#risk.] --><!-- CITATION INCOMPLETE -->
* <cite id="Lichtenstein2000">{{cite book|coauthors=Paul Lichtenstein, Ph.D., Niels V. Holm, M.D., Ph.D., Pia K. Verkasalo, M.D., Ph.D., Anastasia Iliadou, M.Sc., Jaakko Kaprio, M.D., Ph.D., Markku Koskenvuo, M.D., Ph.D., Eero Pukkala, Ph.D., Axel Skytthe, M.Sc., and Kari Hemminki, M.D., Ph.D.|title=Environmental and Heritable Factors in the Causation of Cancer — Analyses of Cohorts of Twins from Sweden, Denmark, and Finland|url=http://content.nejm.org/cgi/content/full/343/2/78|accessdate=2009-01-21|volume=343|year=2000|publisher=New England Journal of Medicine}}</cite>
* <cite id="Montesano2001">{{cite web|url=http://www.journals.elsevierhealth.com/periodicals/ejc/article/PIIS0959804901002660/abstract|title=Environmental causes of human cancers|accessdate=2009-01-21|author=Montesano, R., and Hall, J.|year=2001|publisher=European Journal of Cancer}}</cite>
{{Refend}}
{{Refend}}



Revision as of 09:21, 13 December 2009

The health effects of tobacco are the circumstances, mechanisms, and factors of tobacco consumption on human health. Epidemiological research have been focused primarily on tobacco smoking,[1] which has been studied more extensively than any other form of consumption.[2]

Tobacco use leads most commonly to diseases affecting the heart and lungs, with smoking being a major risk factor for heart attacks, strokes, chronic obstructive pulmonary disease (COPD), emphysema, and cancer (particularly lung cancer, cancers of the larynx and mouth, and pancreatic cancer). It also causes myocardial infarctions, peripheral vascular disease and hypertension, all developed due to the exposure time and the level of dosage of tobacco. Furthermore, the earlier and the higher level of tar content in the tobacco filled cigarettes causes the greater risk of these diseases. Due to higher levels of tar content in third world countries, people who smoke in third world countries are more vulnerable to diseases. Poorer nations also lack the inclusion of filters that richer nations have, however the mortality rate does not show a significant decrease due to filters as many people, filter or no filter, die due to the main reason being their addiction and intake of tobacco.[3]

The World Health Organization estimate that tobacco caused 5.4 million deaths in 2004[4] and 100 million deaths over the course of the 20th century.[5] Similarly, the United States Centers for Disease Control and Prevention describes tobacco use as "the single most important preventable risk to human health in developed countries and an important cause of premature death worldwide."[6]

Smoke contains several carcinogenic pyrolytic products that bind to DNA and cause many genetic mutations. There are over 19 known chemical carcinogens in cigarette smoke. Tobacco also contains nicotine, which is a highly addictive psychoactive chemical. When tobacco is smoked, nicotine causes physical and psychological dependency. Tobacco use is a significant factor in miscarriages among pregnant smokers, it contributes to a number of other threats to the health of the fetus such as premature births and low birth weight and increases by 1.4 to 3 times the chance for Sudden Infant Death Syndrome (SIDS).[7] The result of scientific studies done in neonatal rats seems to indicate that exposure to cigarette smoke in the womb may reduce the fetal brain's ability to recognize hypoxic conditions, thus increasing the chance of accidental asphyxiation.[8] Incidence of impotence is approximately 85 percent higher in male smokers compared to non-smokers,[9] and it is a key cause of erectile dysfunction (ED).[9][10][11]

Epidemiology

Prevalence

While a more general measure of the usage of tobacco (both smoked and smokeless) would be more ideal, the World Health Organization (WHO) reports "data limitations restrict the present indicator to smoked tobacco".[1] Smoking has therefore been studied more extensively than any other form of consumption.[2]

As of 2000, smoking is practiced by 1.22 billion people. Assuming no change in prevalence it is predicted that 1.45 billion people will smoke in 2010 and 1.5 to 1.9 billion in 2025. Assuming that prevalence will decrease at 1% a year and that there will be a modest increase of income of 2%, it is predicted the number of smokers will stand at 1.3 billion in 2010 and 2025.[13]

Smoking is generally five times more prevalent among males than females,[13] however the gender gap declines with younger age.[14][15] In developed countries smoking rates for men have peaked and have begun to decline, however for women they continue to climb.[16]

As of 2002, about twenty percent of young teens (13–15) smoke worldwide. From which 80,000 to 100,000 children begin smoking every day—roughly half of whom live in Asia. Half of those who begin smoking in adolescent years are projected to go on to smoke for 15 to 20 years.[17]

The World Health Organization (WHO) states that "Much of the disease burden and premature mortality attributable to tobacco use disproportionately affect the poor". Of the 1.22 billion smokers, 1 billion of them live in developing or transitional economies. Rates of smoking have leveled off or declined in the developed world.[18] In the developing world, however, tobacco consumption is rising by 3.4% per year as of 2002.[17]

The WHO in 2004 projected 58.8 million deaths to occur globally,[19] from which 5.4 million are tobacco-attributed,[20] and 4.9 million as of 2007.[21] As of 2002, 70% of the deaths are in developing countries.[21]

The shift in prevalence of tobacco smoking to a younger demographic, mainly in the developing world, can be attributed to several factors. The tobacco industry spends up to $12.5 billion dollars annually on advertising, which is increasingly geared towards adolescents in the third world because they are a very vulnerable audience for the marketing campaigns. Adolescents have more difficulty understanding the long term health risks that are associated with smoking and are also more easily influence by “images of romance, success, sophistication, popularity, and adventure which advertising suggests they could achieve through the consumption of cigarettes”. This shift in marketing towards adolescents and even children in the tobacco industry is debilitating to organizations’ and countries’ efforts to improve child health and mortality in the developing world. It reverses or halts the effects of the work that has been done to improve health care in these countries, and although smoking is deemed as a “voluntary” health risk, the marketing of tobacco towards very impressionable adolescents in the developing world makes it less of a voluntary action and more of an inevitable shift.[22]

Studies

In 1938 a study by a John Hopkins University scientist suggested a strongly negative correlation between smoking and lifespan. In 1950 five studies were published in which "smoking was powerfully implicated in the causation of lung cancer".[23] These included the now classic paper "Smoking and Carcinoma of the Lung" which appeared in the British Medical Journal. This paper reported that "heavy smokers were fifty times as likely as non-smokers to contract lung cancer".[23][24]

A team of British scientists headed by Richard Doll carried out a longitudinal study of 34,439 medical specialists from 1951 to 2001, generally called the "British doctors study."[25] The study demonstrated that that about half of the persistent cigarette smokers born in 1900-1909 were eventually killed by their habit (calculated from the logarithms of the probabilities of surviving from 35-70, 70-80, and 80-90) and about two thirds of the persistent cigarette smokers born in the 1920s would eventually be killed by their habit. After a ban on smoking in all enclosed public places was introduced in Scotland in March 2006, there was a 17 percent reduction in hospital admissions for acute coronary syndrome. 67% of the decrease occurred in non-smokers.[26]

The health effects of tobacco have been significant for the development of the science of epidemiology. As the mechanism of carcinogenicity is radiomimetic or radiological, the effects are stochastic. Definite statements can be made only on the relative increased or decreased probabilities of contracting a given disease; Philosophically and theoretically speaking, it is impossible to definitively prove a direct causative link between exposure to a radiomimetic poison such as tobacco smoke and the cancer that follows. Tobacco companies have capitalized on this philosophical objection and exploited the doubts of clinicians, who consider only individual cases, on the causal link in the stochastic expression of the toxicity as actual disease.[27]

There have been multiple court cases on the issue that tobacco companies have researched the health effects of tobacco, but suppressed the findings or formatted them to imply lessened or no hazard.[27]

A study published in the journal Pediatrics[28] refers to the danger posed by what the authors call "third-hand smoke" — toxic substances that remain in areas where smoking has recently occurred. The study was reviewed in an story broadcast by the Voice of America.

Occasional Smoking

The term "smoker" is used to mean a person who habitually smokes tobacco on a daily basis. This category has been the focus of the vast majority of tobacco studies. However, the health effects of less-than-daily smoking are far less well understood. Studies have often taken the data of "occasional smokers" (those who have never smoked daily) and grouped them with those who have never smoked.[29]

A recent European study on occasional smoking published findings that the risk of the major smoking-related cancers was 1.24 times higher for occasional smokers than for those who have never smoked at all. (For a confidence interval of 95%, this data showed an incidence rate ratio of 0.80 to 1.94.)[29] This compares to studies showing that habitual heavy smokers have greater than 50 times the incidence of smoking-related cancers.

Mechanism

Chemical carcinogens

Smoke, or any partially burnt organic matter, is carcinogenic (cancer-causing). The damage a continuing smoker does to their lungs can take up to 20 years before its physical manifestation in lung cancer. Women began smoking later than men, so the rise in death rate amongst women did not appear until later. The male lung cancer death rate decreased in 1975 — roughly 20 years after the fall in cigarette consumption in men. A fall in consumption in women also began in 1975 but by 1991 had not manifested in a decrease in lung cancer related mortalities amongst women.[31]

Smoke contains several carcinogenic pyrolytic products that bind to DNA and cause genetic mutations. Particularly potent carcinogens are polynuclear aromatic hydrocarbons (PAH), which are toxicated to mutagenic epoxides. The first PAH to be identified as a carcinogen in tobacco smoke was benzopyrene, which has been shown to toxicate into an epoxide that irreversibly attaches to a cell's nuclear DNA, which may either kill the cell or cause a genetic mutation. If the mutation inhibits programmed cell death, the cell can survive to become a cancer cell. Similarly, acrolein, which is abundant in tobacco smoke, also irreversibly binds to DNA, causes mutations and thus also cancer. However, it needs no activation to become carcinogenic.[32]

There are over 19 known carcinogens in cigarette smoke.[33] The following are some of the most potent carcinogens:

  • Polynuclear aromatic hydrocarbons are tar components produced by pyrolysis in smoldering organic matter and emitted into smoke. Many of them are highly carcinogenic and mutagenic, because they are toxicated to mutagenic epoxides, which are electrophilic alkylating agents. The first PAH to be identified as a carcinogen in tobacco smoke was benzopyrene, which been shown to toxicate into a diol epoxide and then permanently attach to nuclear DNA, which may either kill the cell or cause a genetic mutation. The DNA contains the information on how the cell function; in practice, it contains the recipes for protein synthesis. If the mutation inhibits programmed cell death, the cell can survive to become a cancer cell, a cell that does not function like a normal cell. The carcinogenity is radiomimetic, i.e. similar to that produced by ionizing nuclear radiation. Tobacco manufacturers have experimented with combustionless vaporizer technology to allow cigarettes to be consumed without the formation of carcinogenic benzopyrenes.[34] However, such products have not become popular.
  • Acrolein is a pyrolysis product that is abundant in cigarette smoke. It gives smoke an acrid smell and an irritating, lachromatory effect and is a major contributor to its carcinogenity. Like PAH metabolites, acrolein is also an electrophilic alkylating agent and permanently binds to the DNA base guanine, by a conjugate addition followed by cyclization into a hemiaminal. The acrolein-guanine adduct induces mutations during DNA copying and thus causes cancers in a manner similar to PAHs. However, acrolein is 1000 times more abundant than PAHs in cigarette smoke, and is able to react as is, without metabolic activation. Acrolein has been shown to be a mutagen and carcinogen in human cells. The carcinogenity of acrolein has been difficult to study by animal experimentation, because it has such a toxicity that it tends to kill the animals before they develop cancer.[32] Generally, compounds able to react by conjugate addition as electrophiles (so-called Michael acceptors after Michael reaction) are toxic and carcinogenic, because they can permanently alkylate DNA, similarly to mustard gas or aflatoxin. Acrolein is only one of them present in cigarette smoke; for example, crotonaldehyde has been found in cigarette smoke.[35] Michael acceptors also contribute to the chronic inflammation present in tobacco disease.[36]
  • Nitrosamines are a group of carcinogenic compounds found in cigarette smoke but not in uncured tobacco leaves. Nitrosamines form on flue-cured tobacco leaves during the curing process through a chemical reaction between nicotine and other compounds contained in the uncured leaf and various oxides of nitrogen found in all combustion gases. Switching to indirect-fire curing has been shown to reduce nitrosamine levels to less than 0.1 parts per million.[37][38]

Radioactive carcinogens

In addition to chemical, nonradioactive carcinogens, tobacco and tobacco smoke contain small amounts of lead-210 (210Pb) and polonium-210 (210Po) both of which are radioactive carcinogens. The presence of polonium-210 in mainstream cigarette smoke has been experimentally measured at levels of 0.0263–0.036 pCi (0.97–1.33 mBq),[39] which is equivalent to about 0.1 pCi per milligram of smoke (4 mBq/mg); or about 0.81 pCi of lead 210 per gram of dry condensed smoke (30 Bq/kg).

Research by NCAR radiochemist Ed Martell determined that radioactive compounds in cigarette smoke are deposited in "hot spots" where bronchial tubes branch. Since tar from cigarette smoke is resistant to dissolving in lung fluid, the radioactive compounds have a great deal of time to undergo radioactive decay before being cleared by natural processes. Indoors, these radioactive compounds linger in secondhand smoke, and therefore greater exposure occurs when these radioactive compounds are inhaled during normal breathing, which is deeper and longer than when inhaling cigarettes. Damage to the protective epithelial tissue from smoking only increases the prolonged retention of insoluble polonium 210 compounds produced from burning tobacco. Martell estimated that a carcinogenic radiation dose of 80-100 rads is delivered the lung tissue of most smokers who die of lung cancer.[40]

The view that polonium 210 is responsible for many cases of cancer in tobacco smokers is disputed by at least one researcher.[41][42]

Nicotine

Nicotine molecule

Nicotine that is contained in cigarettes and other smoked tobacco products is a stimulant and is one of the main factors leading to continued tobacco smoking. Although the amount of nicotine inhaled with tobacco smoke is quite small (most of the substance is destroyed by the heat) it is still sufficient to cause physical and/or psychological dependence. The amount of nicotine absorbed by the body from smoking depends on many factors, including the type of tobacco, whether the smoke is inhaled, and whether a filter is used. Despite the design of various cigarettes advertised and even tested on machines to deliver less of the toxic tar, studies show that when smoked by humans instead of machines, they deliver the same net amount of smoke. Ingesting a compound by smoking is one of the most rapid and efficient methods of introducing it into the bloodstream, second only to injection, which allows for the rapid feedback which supports the smokers' ability to titrate their dosage. On average it takes about ten seconds for the substance to reach the brain. As a result of the efficiency of this delivery system, many smokers feel as though they are unable to cease. Of those who attempt cessation and last three months without succumbing to nicotine, most are able to remain smoke free for the rest of their lives.[43] There exists a possibility of depression in some who attempt cessation, as with other psychoactive substances. Depression is also common in teenage smokers; teens who smoke are four times as likely to develop depressive symptoms as their nonsmoking peers.[44]

Although nicotine does play a role in acute episodes of some diseases (including stroke, impotence, and heart disease) by its stimulation of adrenaline release, which raises blood pressure,[45] heart rate, and free fatty acids, the most serious longer term effects are more the result of the products of the smouldering combustion process. This has enabled development of various nicotine delivery systems, such as the nicotine patch or nicotine gum, that can satisfy the addictive craving by delivering nicotine without the harmful combustion by-products. This can help the heavily dependent smoker to quit gradually, while discontinuing further damage to health.

Nicotine is a highly addictive psychoactive chemical. When tobacco is smoked, most of the nicotine is pyrolyzed; a dose sufficient to cause mild somatic dependency and mild to strong psychological dependency remains. There is also a formation of harmane (a MAO inhibitor) from the acetaldehyde in cigarette smoke, which seems to play an important role in nicotine addiction[46] probably by facilitating dopamine release in the nucleus accumbens in response to nicotine stimuli. According to studies by Henningfield and Benowitz, nicotine is more addictive than cannabis, caffeine, ethanol, cocaine, and heroin when considering both somatic and psychological dependence. However, due to the stronger withdrawal effects of ethanol, cocaine and heroin, nicotine may have a lower potential for somatic dependence than these substances.[47][48] A study by Perrine concludes that nicotine's potential for psychological dependency exceeds all other studied drugs[citation needed] - even ethanol, an extremely physically addictive substance with severe withdrawal symptoms that can be fatal. About half of Canadians who currently smoke have tried to quit.[49] McGill University health professor Jennifer O'Loughlin stated that nicotine addiction can occur as soon as five months after the start of smoking.[50]

Recent evidence has shown that smoking tobacco increases the release of dopamine in the brain, specifically in the mesolimbic pathway, the same neuro-reward circuit activated by drugs of abuse such as heroin and cocaine. This suggests nicotine use has a pleasurable effect that triggers positive reinforcement.[51] One study found that smokers exhibit better reaction-time and memory performance compared to non-smokers, which is consistent with increased activation of dopamine receptors.[52] Neurologically, rodent studies have found that nicotine self-administration causes lowering of reward thresholds—a finding opposite that of most other drugs of abuse (e.g. cocaine and heroin). This increase in reward circuit sensitivity persisted months after the self-administration ended, suggesting that nicotine's alteration of brain reward function is either long lasting or permanent. Furthermore, it has been found that nicotine can activate long term potentiation in vivo and in vitro. These studies suggests nicotine’s "trace memory" may contribute to difficulties in nicotine abstinence.

The carcinogenity of tobacco smoke is not explained by nicotine per se, which is not carcinogenic or mutagenic. However, it inhibits apoptosis, therefore accelerating existing cancers.[53] Also, NNK, a nicotine derivative converted from nicotine, can be carcinogenic.

It is worth noting that nicotine, although frequently implicated in producing tobacco addiction, is not significantly addictive when administered alone.[54] The addictive potential manifests itself after co-administration of an MAOI, which specifically causes sensitization of the locomotor response in rats, a measure of addictive potential.[55]

Genetic

According to three separate studies commissioned by governments in the US and Europe, scientists have identified a genetic link that makes people more likely to become addicted to tobacco. This genetic variation causes individuals to smoke more cigarettes, makes it harder for them to quit and increases their likelihood of developing lung cancer by up to 80%.[56]

Genetic markers of more than 35,000 people (mostly smokers and ex-smokers) were surveyed by scientists in three separate studies, and all three found lung cancer to be associated with similar sets of genetic differences. The genetic variations of note encode nicotine receptors on cells and were identified on a region of chromosome 15.[57] Possessing a single copy of the mutation raises an individual's risk of lung cancer by approximately 30%; for two copies the increase is about 80%. The gene was found to be attributable to 14% of lung cancer cases, and it was found to confer similar lung cancer risks irrespective of smoking status or quantity smoked.[58]

Another study related to genetic changes in smokers was conducted by Wan L Lam and Stephen Lam from the BC Cancer Agency, in 2007. The study revealed that cigarette smoke can turn on or off some of the genes, which otherwise would remain inactive. Some changes on genetic level could be reversed after the smoking was quit, yet others could not. Examples of reversible genes involved the so-called xenofobic functions, nucleotide metabolism and mucus secretion. Smoking turns off some DNA repair genes that cannot be reversed. It also switches off permanently some genes responsible from protection from cancer growth in the body.[59]

Health effects

Summary of tobacco related diseases. Click to enlarge

Most scientists involved in cancer research believe that the environmental factors, which include anything the people interact with such as lifestyle choices, their diet, natural and medical radiation, sunlight exposure, workplace exposure, and socioeconomic factors that affect exposures and susceptibility—may be a major contributor to the development of cancer.[60] Other factors that play a major role in cancer development are infectious diseases, aging, and individual susceptibility such as genetic predisposition.[61] Because of these confounding variables, it is difficult to distinguish which factor or condition contributes to the development of cancer. For example, smoking tobacco is known to cause cancer in humans, but not all people who smoke develop smoking-related cancer; however, with some substances or exposure circumstances, cancer may develop after even brief exposure.[62]

A person's increased risk of contracting disease is directly proportional to the length of time that a person continues to smoke as well as the amount smoked. However, if someone stops smoking, then these chances gradually decrease as the damage to their body is repaired. A year after quitting, the risk of contracting heart disease is half that of a continuing smoker.[63] The health risks of smoking are not uniform across all smokers. Risks vary according to amount of tobacco smoked, with those who smoke more at greater risk. Light smoking is still a health risk. Likewise, smoking "light" cigarettes does not reduce the risks.

Tobacco use most commonly leads to diseases affecting the heart and lungs, with smoking being a major risk factor for heart attacks, Chronic Obstructive Pulmonary Disease (COPD), emphysema, and cancer, particularly lung cancer, cancers of the larynx and mouth, and pancreatic cancer. Overall life expectancy is also reduced in regular smokers, with estimates ranging from 10[64] to 17.9 [65] years fewer than nonsmokers.[66] About two thirds of male smokers will die of illness due to smoking.[67] The association of smoking with lung cancer is strongest, both in the public perception and etiologically. People who have smoked tobacco at some point have about a one in ten chance of developing lung cancer during their lifetime.[68] If one looks at men who continue to smoke tobacco, the risk increases to one in six.[69] Historically, lung cancer was considered to be a rare disease prior to World War I and was perceived as something most physicians would never see during their career. With the postwar rise in popularity of cigarette smoking came a virtual epidemic of lung cancer.[70][71]

A person's increased risk of contracting disease is directly proportional to the length of time that a person smokes, as well as to the amount smoked, and doctors use the approximation "pack years" in assessing the likelihood of smoking-related illness. However, if someone stops smoking, then their risk declines over time,[43] and the reduction in their lung function will stop.

Mortality

Male and female smokers lose an average of 13.2 and 14.5 years of life, respectively.[72]

According to the results of a 50 year study of 34,439 male British doctors, at least half of all lifelong smokers die earlier as a result of smoking.[73]

Smokers are triple as likely of dying before the age of 70.[74][75][76]


In the United States alone, cigarette smoking and exposure to tobacco smoke results in at least 443,000 premature deaths annually.[77]

In the United States alone, tobacco kills the equivalent of three jumbo jets full of people crashing every day, with no survivors, 365 days of the year. -ABC's Peter Jennings[78] On a worldwide basis, it's 1 jumbo jet per hour, 24 hours a day, 365 days of the year. -WHO [79]

Cancer

The primary risks of tobacco usage include many forms of cancer, particularly lung cancer,[80] cancer of the kidney,[81] cancer of the larynx and head and neck, breast cancer,[82][83] bladder,[84] esophagus, pancreas,[85] and stomach.[86] There is some evidence suggesting an increased risk of myeloid leukemia, squamous cell sinonasal cancer, liver cancer, cervical cancer, colorectal cancer after an extended latency, childhood cancers and cancers of the gall bladder, adrenal gland and small intestine.

Lung Cancer

The risk of dying from lung cancer before age 85 is 22.1% for a male smoker and 11.9% for a female current smoker, in the absence of competing causes of death. The corresponding estimates for lifelong nonsmokers are a 1.1% probability of dying from lung cancer before age 85 for a man of European descent, and a 0.8% probability for a woman\[87]

Pulmonary

Since establishing causation through experimental trials was not possible due to ethical restrictions, a lengthy study was conducted in order to establish the strong association necessary to allow for legislative action against tobacco consumption.[citation needed]

In smoking, long term exposure to compounds found in the smoke such as carbon monoxide, cyanide, and so forth—, are believed to be responsible for pulmonary damage and for loss of elasticity in the alveoli, leading to emphysema and COPD. The carcinogen acrolein and its derivatives also contribute to the chronic inflammation present in COPD.[36]

Secondhand smoke is a mixture of smoke from the burning end of a cigarette, pipe or cigar and the smoke exhaled from the lungs of smokers. It is involuntarily inhaled, lingers in the air hours after cigarettes have been extinguished, and can cause a wide range of adverse health effects, including cancer, respiratory infections, and asthma.[88] Nonsmokers who are exposed to secondhand smoke at home or work increase their heart disease risk by 25–30% and their lung cancer risk by 20–30%. Secondhand smoke has been estimated to cause 38,000 deaths per year, of which 3,400 are deaths from lung cancer in non-smokers.[89]

Chronic obstructive pulmonary disease (COPD) caused by smoking, known as tobacco disease, is a permanent, incurable reduction of pulmonary capacity characterized by shortness of breath, wheezing, persistent cough with sputum, and damage to the lungs, including emphysema and chronic bronchitis.[90]

Influenza

A study of an outbreak of A(H1N1) influenza in an Israeli military unit of 336 healthy young men to determine the relation of cigarette smoking to the incidence of clinically apparent influenza, revealed that, of 168 smokers, 68.5 percent had influenza, as compared with 47.2 percent of nonsmokers. Influenza was also more severe in the smokers; 50.6 percent of the smokers lost work days or required bed rest, or both, as compared with 30.1 percent of the nonsmokers[91].

According to a study of 1,900 male cadets after the 1968 Hong Kong A2 influenza epidemic at a South Carolina military academy, compared with nonsmokers heavy smokers (more than 20 cigarettes per day), had 21% more illnesses and 20% more bed rest, light smokers (less than 20 cigarettes per day) had 10% more illnesses and 7% more bed rest[92].

The effect of cigarette smoking upon epidemic influenza was studied prospectively among 1,811 male college students. Clinical influenza incidence among those who daily smoked 21 or more cigarettes was 21% higher than that of non-smokers. Influenza incidence among smokers of 1 to 20 cigarettes daily was intermediate between non-smokers and heavy cigarette smokers[93].

Surveillance of a 1979 influenza out-break at a military base for women in Israel revealed that, Influenza symptoms developed in 60.0% of the current smokers vs. 41.6% of the nonsmokers[94].

Smoking seems to cause a higher relative influenza-risk in older populations than in younger populations. In a prospective study of community-dwelling people 60–90 years of age, during 1993, of unimmunized people 23% of smokers had clinical influenza as compared with 6 % of non-smokers[95].

Smoking may substantially contribute to the growth of influenza epidemics affecting the entire population[91]. However the proportion of influenza cases in the general non-smoking population attributable to smokers has not yet been calculated.

Cardiovascular

Inhalation of tobacco smoke causes several immediate responses within the heart and blood vessels. Within one minute the heart rate begins to rise, increasing by as much as 30 percent during the first 10 minutes of smoking. Carbon monoxide in tobacco smoke exerts its negative effects by reducing the blood’s ability to carry oxygen.[96]

Smoking also increases the chance of heart disease, stroke, atherosclerosis, and peripheral vascular disease. Several ingredients of tobacco lead to the narrowing of blood vessels, increasing the likelihood of a blockage, and thus a heart attack or stroke. According to a study by an international team of researchers, people under 40 are five times more likely to have a heart attack if they smoke.[97]

Latest research of the American biologists have determined that cigarette smoke also influences the process of cell division in the cardiac muscle and changes heart's shape.[98]

The usage of tobacco has also been linked to Buerger's disease (thromboangiitis obliterans) the acute inflammation and thrombosis (clotting) of arteries and veins of the hands and feet.[citation needed]

The current Surgeon General’s Report concluded that there is no risk-free level of exposure to secondhand smoke. Even short exposures to secondhand smoke can cause blood platelets to become stickier, damage the lining of blood vessels, decrease coronary flow velocity reserves, and reduce heart rate variability, potentially increasing the risk of heart attack. New research indicates that private research conducted by cigarette company Philip Morris in the 1980s showed that secondhand smoke was toxic, yet the company suppressed the finding during the next two decades.[88]

Although cigarette smoking causes a greater increase of the risk of cancer than cigar smoking, cigar smokers still have an increased risk for many health problems, including cancer, when compared to non-smokers.[99][100] As for Environmental Tobacco Smoke (ETS, or "Second-hand Smoking"), the NIH study points to the large amount of smoke generated by one cigar, saying "cigars can contribute substantial amounts of tobacco smoke to the indoor environment; and, when large numbers of cigar smokers congregate together in a cigar smoking event, the amount of ETS produced is sufficient to be a health concern for those regularly required to work in those environments."[101]

Smoking tends to increase blood cholesterol levels. Furthermore, the ratio of high-density lipoprotein (the "good" cholesterol) to low-density lipoprotein (the "bad" cholesterol) tends to be lower in smokers compared to non-smokers. Smoking also raises the levels of fibrinogen and increases platelet production (both involved in blood clotting) which makes the blood viscous. Carbon monoxide binds to haemoglobin (the oxygen-carrying component in red blood cells), resulting in a much stabler complex than haemoglobin bound with oxygen or carbon dioxide—the result is permanent loss of blood cell functionality. Blood cells are naturally recycled after a certain period of time, allowing for the creation of new, functional erythrocytes. However, if carbon monoxide exposure reaches a certain point before they can be recycled, hypoxia (and later death) occurs. All these factors make smokers more at risk of developing various forms of arteriosclerosis. As the arteriosclerosis progresses, blood flows less easily through rigid and narrowed blood vessels, making the blood more likely to form a thrombosis (clot). Sudden blockage of a blood vessel may lead to an infarction (e.g. stroke). However, it is also worth noting that the effects of smoking on the heart may be more subtle. These conditions may develop gradually given the smoking-healing cycle (the human body heals itself between periods of smoking), and therefore a smoker may develop less significant disorders such as worsening or maintenance of unpleasant dermatological conditions, e.g. eczema, due to reduced blood supply. Smoking also increases blood pressure and weakens blood vessels.[102]

Oral

Perhaps the most serious oral condition that can arise is that of oral cancer. However, smoking also increases the risk for various other oral diseases, some almost completely exclusive to tobacco users. The National Institutes of Health, through the National Cancer Institute, determined in 1998 that "cigar smoking causes a variety of cancers including cancers of the oral cavity (lip, tongue, mouth, throat), esophagus, larynx, and lung."[101] Pipe smoking involves significant health risks,[103][104] particularly oral cancer.[105][106] Roughly half of periodontitis or inflammation around the teeth cases attributed to current or former smoking. Smokeless tobacco causes gingival recession and white mucosal lesions. Up to 90% of periodontitis patients who are not helped by common modes of treatment are smokers. Smokers have significantly greater loss of bone height than nonsmokers, and the trend can be extend to pipe smokers to have more bone loss than nonsmokers.[107] Smoking has been proven to be an important factor in the staining of teeth.[108][109] Halitosis or bad breath is common among tobacco smokers[110]. Tooth loss has been shown to be 2[111] to 3 times[112] higher in smokers than in non-smokers.[113] In addition, complications may further include leukoplakia the adherent white plaques or patches on the mucous membranes of the oral cavity, including the tongue, and a loss of taste sensation or salivary changes.[citation needed]

Infection

Tobacco is also linked to susceptibility to infectious diseases, particularly in the lungs. Smoking more than 20 cigarettes a day increases the risk of tuberculosis by two to four times,[114][115] and being a current smoker has been linked to a fourfold increase in the risk of invasive pneumococcal disease.[116] It is believed that smoking increases the risk of these and other pulmonary and respiratory tract infections both through structural damage and through effects on the immune system. The effects on the immune system include an increase in CD4+ cell production attributable to nicotine, which has tentatively been linked to increased HIV susceptibility.[117] The usage of tobacco also increases rates of infection: common cold and bronchitis, chronic obstructive pulmonary disease, emphysema and chronic bronchitis in particular.[citation needed]

Smoking reduces the risk of Kaposi's sarcoma in people without HIV infection.[118]

Impotence

In a study of men ages 24 to 36 seeking treatment for infertility, Panayiotis Zavos, Ph.D., confirmed the results of earlier studies demonstrating that smoking harms sperm quality in every way, from longevity to motility. But Zavos also found that smoking affected sexual behavior. The smokers had sex an average of 5.7 times per month, while the nonsmokers reported an average of 11.6 encounters. And on a scale of 1 to 10, the smokers rated the quality of sex at a lackluster 5.2, compared to 8.7 for nonsmokers."[119]

Psychological

Immediate Effects

Smokers report a variety of physical and psychological effects from smoking tobacco. Those new to smoking may experience nausea, dizziness, and rapid heart beat. The unpleasant symptoms will eventually vanish over time, with repeated use, as the body builds a tolerance to the chemicals in the cigarettes, such as nicotine.

Cognitive Function

The usage of tobacco also creates cognitive dysfunction, which include: increased risk (or decrease)[120] of Alzheimer's disease and decline in cognitive abilities,[121] reduced memory and cognitive abilities in adolescent smokers,[122] brain shrinkage (cerebral atrophy)[123][124]

In many respects, nicotine acts on the nervous system in a similar way to caffeine. Some writings have stated that smoking can also increase mental concentration; one study documents a significantly better performance on the normed Advanced Raven Progressive Matrices test after smoking.[125]

Most smokers, when denied access to nicotine, exhibit symptoms such as irritability, jitteriness, dry mouth, and rapid heart beat.[126] The onset of these symptoms is very fast, nicotine's half-life being only 2 hours. Withdrawal symptoms can appear even if the smoker's consumption is very limited or irregular, appearing after only 4-5 cigarettes in most adolescents. An ex-smoker's chemical dependence to nicotine will cease after approximately ten to twenty days, although the brain's number of nicotine receptors is permanently altered,[127] and the psychological dependence may linger for months or even many years. Unlike some recreational drugs, nicotine does not measurably alter a smoker's motor skills, judgement, or language abilities while under the influence of the drug. Tobacco withdrawal has been shown to cause clinically significant distress.[128]

Most notably, some studies have found that patients with Alzheimer's disease are more likely not to have smoked than the general population, which has been interpreted to suggest that smoking offers some protection against Alzheimer's. However, the research in this area is limited and the results are conflicting; some studies show that smoking increases the risk of Alzheimer's disease. A recent review of the available scientific literature concluded that the apparent decrease in Alzheimer risk may be simply due to the fact that smokers tend to die before reaching the age at which Alzheimer normally occurs. "Differential mortality is always likely to be a problem where there is a need to investigate the effects of smoking in a disorder with very low incidence rates before age 75 years, which is the case of Alzheimer's disease," it stated, noting that smokers are only half as likely as non-smokers to survive to the age of 80.[120]

Former and current smokers have a lower incidence of Parkinson's disease compared to people who have never smoked,[129][130] although the authors stated that it was more likely that the movement disorders which are part of Parkinson's disease prevented people from being able to smoke than that smoking itself was protective. Another study considered a possible role of nicotine in reducing Parkinson's risk: nicotine stimulates the dopaminergic system of the brain, which is damaged in Parkinson's disease, while other compounds in tobacco smoke inhibit MAO-B, an enzyme which produces oxidative radicals by breaking down dopamine.[131]

A very large percentage of schizophrenics smoke tobacco as a form of self medication.[132][133][134][135] The high rate of tobacco use by the mentally ill is a major factor in their decreased life expectancy, which is about 25 years shorter than the general population.[136] Following the observation that smoking improves condition of people with schizophrenia, in particular working memory deficit, nicotine patches had been proposed as a way to treat schizophrenia.[137] Some studies suggest that a link exists between smoking and mental illness, citing the high incidence of smoking amongst those suffering from schizophrenia[138] and the possibility that smoking may alleviate some of the symptoms of mental illness,[139] but these have not been conclusive.

Recent studies have linked smoking to anxiety disorders, suggesting the correlation (and possibly mechanism) may be related to the broad class of anxiety disorders, and not limited to just depression. Current ongoing research are attempting to explore the addiction-anxiety relationship.

Data from multiple studies suggest that anxiety disorders and depression play a role in cigarette smoking.[140] A history of regular smoking was observed more frequently among individuals who had experienced a major depressive disorder at some time in their lives than among individuals who had never experienced major depression or among individuals with no psychiatric diagnosis.[141] People with major depression are also much less likely to quit due to the increased risk of experiencing mild to severe states of depression, including a major depressive episode.[142] Depressed smokers appear to experience more withdrawal symptoms on quitting, are less likely to be successful at quitting, and are more likely to relapse.[143]

Evidence suggests that non-smokers are up to twice as likely as smokers to develop Parkinson's disease or Alzheimer's disease.[144] A plausible explanation for these cases may be the effect of nicotine, a cholinergic stimulant, decreasing the levels of acetylcholine in the smoker's brain; Parkinson's disease occurs when the effect of dopamine is less than that of acetylcholine. In addition, nicotine stimulates the mesolimbic dopamine pathway (as do other drugs of abuse), causing an effective increase in dopamine levels. Opponents counter by noting that consumption of pure nicotine may be as beneficial as smoking without the risks associated with smoking, although this is unlikely due to the importance of the MAO-B inhibitor compounds of tobacco in preventing neurodegenerative diseases.

In pregnancy

A number of studies have shown that tobacco use is a significant factor in miscarriages among pregnant smokers, and that it contributes to a number of other threats to the health of the fetus.[145][146] Second-hand smoke appears to present an equal danger to the fetus, as one study noted that "heavy paternal smoking increased the risk of early pregnancy loss."[147]

Other

Studies suggest that smoking decreases appetite, but did not conclude that overweight people should smoke or that their health would improve by smoking.[148][149] Smoking also decreases weight by overexpressing the gene AZGP1 which stimulates lipolysis.[150]

Preliminary reports suggest that smoking can decrease the incidence of acne prophylactically. This was seen by a decreased percentage ratio of patients needing acne medication versus the percentage of entire population of smokers. (A smaller percentage of patients who smoked needed medication than found in the population as a whole).[151]

A protective effect of current smoking against ulcerative colitis, although smoking increases the risk of Crohn's disease, the other form of inflammatory bowel disease.[152] There is some evidence for decreased rates of endometriosis in infertile smoking women,[153] although other studies have found that smoking increases the risk in infertile women.[154] There is little or no evidence of a protective effect in fertile women. Some preliminary data from 1996 suggested a reduced incidence of uterine fibroids,[155] but overall the evidence is unconvincing.[156]

A new research has found that women who smoke are at significantly increased risk of developing an abdominal aortic aneurysm, a condition in which a weak area of the abdominal aorta expands or bulges.[157]

Several types of "Smoker’s Paradoxes",[158] (cases where smoking appears to have specific beneficial effects), have been observed; often the actual mechanism remains undetermined. Risk of ulcerative colitis has been frequently shown to be reduced by smokers on a dose-dependent basis; the effect is eliminated if the individual stops smoking.[159][160] Smoking appears to interfere with development of Kaposi's sarcoma,[161] breast cancer among women carrying the very high risk BRCA gene,[162] preeclampsia,[163] and atopic disorders such as allergic asthma.[164] A plausible mechanism of action in these cases may be the nicotine in tobacco smoke acting as an anti-inflammatory agent and interfering with the disease process.[165]

History

The late-19th century invention of automated cigarette-making machinery in the American South made possible mass production of cigarettes at low cost, and cigarettes became elegant and fashionable among society men as the Victorian era gave way to the Edwardian. In 1912, American Dr. Isaac Adler was the first to strongly suggest that lung cancer is related to smoking.[166] In 1929, Fritz Lickint of Dresden, Germany, published a formal statistical evidence of a lung cancer–tobacco link, based on a study showing that lung cancer sufferers were likely to be smokers.[167] Lickint also argued that tobacco use was the best way to explain the fact that lung cancer struck men four or five times more often than women (since women smoked much less).[167]

Prior to World War I, lung cancer was considered to be a rare disease, which most physicians would never see during their career.[168][169] With the postwar rise in popularity of cigarette smoking, however, came an epidemic of lung cancer.

In 1950, Richard Doll published research in the British Medical Journal showing a close link between smoking and lung cancer.[170] Four years later, in 1954 the British Doctors Study, a study of some 40 thousand doctors over 20 years, confirmed the suggestion, based on which the government issued advice that smoking and lung cancer rates were related.[171] The British Doctors Study lasted till 2001, with results published every ten years and final results published in 2004 by Doll and Richard Peto.[172] Much early research was also done by Alton Ochsner. Reader's Digest magazine for many years published frequent anti-smoking articles. In 1964 the United States Surgeon General's Report on Smoking and Health (referenced below), led millions of American smokers to quit, the banning of certain advertising, and the requirement of warning labels on tobacco products.

The Canadian province of British Columbia has the Tobacco Damages and Health Care Costs Recovery Act.

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