Pack year
A pack year is a quantification of cigarette smoking.
Contents |
[edit] Definition
A way to measure the amount a person has smoked over a long period of time. It is calculated by multiplying the number of packs of cigarettes smoked per day by the number of years the person has smoked. For example, 1 pack year is equal to smoking 20 cigarettes (1 pack) per day for 1 year, or 40 cigarettes per day for half a year, and so on.[1]
One pack year equals 365 packs of cigarettes.
[edit] Calculation
Number of Pack Years = (Packs smoked per day) × (years as a smoker)
or
Number of pack years = (number of cigarettes smoked per day × number of years smoked)/20 (1 pack has 20 cigarettes).
For example: a patient who has smoked 15 cigarettes a day for 40 years has a (15×40)/20 = 30 pack year smoking history.
A pack-year is smoking 20 cigarettes a day for one year. If someone has smoked ten cigarettes a day for six years they would have a three pack-year history. Someone who has smoked forty cigarettes daily for twenty years has a forty pack-year history.
Someone who has a 14 pack-year history of smoking (the equivalent of 1 pack of cigarettes per day for 14 years) has smoked over 100,000 cigarettes.
[edit] Significance and usage
Quantification of pack years smoked is important in clinical care where degree of tobacco exposure is closely correlated to risk of disease.
[edit] References
- ^ http://www.cancer.gov/dictionary?CdrID=306510 National Cancer Institute definition of pack year
