Population health has been defined as "the health outcomes of a group of individuals, including the distribution of such outcomes within the group". It is an approach to health that aims to improve the health of an entire human population. This concept does not refer to animal or plant populations. A priority considered important in achieving this aim is to reduce health inequities or disparities among different population groups due to, among other factors, the social determinants of health, SDOH. The SDOH include all the factors: social, environmental, cultural and physical the different populations are born into, grow up and function with throughout their lifetimes which potentially have a measurable impact on the health of human populations. The Population Health concept represents a change in the focus from the individual-level, characteristic of most mainstream medicine. It also seeks to complement the classic efforts of public health agencies by addressing a broader range of factors shown to impact the health of different populations. The World Health Organization's Commission on Social Determinants of Health, reported in 2008, that the SDOH factors were responsible for the bulk of diseases and injuries and these were the major causes of health inequities in all countries. In the US, SDOH were estimated to account for 70% of avoidable mortality.
From a population health perspective, health has been defined not simply as a state free from disease but as "the capacity of people to adapt to, respond to, or control life's challenges and changes".The World Health Organization (WHO) defined health in its broader sense in 1946 as "a state of complete physical, mental, and social well-being and not merely the absence of disease or infirmity."
Healthy People 2020
Healthy People 2020 is a web site sponsored by the US Department of Health and Human Services, representing the cumulative effort of 34 years of interest by the Surgeon General's office and others. It identifies 42 topics considered Social determinants of health and approximately 1200 specific goals considered to improve population health. It provides links to the current research available for selected topics and identifies and supports the need for community involvement considered essential to address these problems realistically.
The role of economic inequality
Recently, there has been increasing interest from epidemiologists on the subject of economic inequality and its relation to the health of populations. There is a very robust correlation between socioeconomic status and health. This correlation suggests that it is not only the poor who tend to be sick when everyone else is healthy, heart disease, ulcers, type 2 diabetes, rheumatoid arthritis, certain types of cancer, and premature aging. Despite the reality of the SES Gradient, there is debate as to its cause. A number of researchers (A. Leigh, C. Jencks, A. Clarkwest—see also Russell Sage working papers) see a definite link between economic status and mortality due to the greater economic resources of the better-off, but they find little correlation due to social status differences.
Other researchers such as Richard G. Wilkinson, J. Lynch, and G.A. Kaplan have found that socioeconomic status strongly affects health even when controlling for economic resources and access to health care. Most famous for linking social status with health are the Whitehall studies—a series of studies conducted on civil servants in London. The studies found that, despite the fact that all civil servants in England have the same access to health care, there was a strong correlation between social status and health. The studies found that this relationship stayed strong even when controlling for health-affecting habits such as exercise, smoking and drinking. Furthermore, it has been noted that no amount of medical attention will help decrease the likelihood of someone getting type 1 diabetes or rheumatoid arthritis—yet both are more common among populations with lower socioeconomic status. Lastly, it has been found that amongst the wealthiest quarter of countries on earth (a set stretching from Luxembourg to Slovakia) there is no relation between a country's wealth and general population health—suggesting that past a certain level, absolute levels of wealth have little impact on population health, but relative levels within a country do. The concept of psychosocial stress attempts to explain how psychosocial phenomenon such as status and social stratification can lead to the many diseases associated with the SES gradient. Higher levels of economic inequality tend to intensify social hierarchies and generally degrades the quality of social relations—leading to greater levels of stress and stress related diseases. Richard Wilkinson found this to be true not only for the poorest members of society, but also for the wealthiest. Economic inequality is bad for everyone's health. Inequality does not only affect the health of human populations. David H. Abbott at the Wisconsin National Primate Research Center found that among many primate species, less egalitarian social structures correlated with higher levels of stress hormones among socially subordinate individuals. Research by Robert Sapolsky of Stanford University provides similar findings.
There is well-documented variation in health outcomes and health care utilization & costs by geographic variation in the U.S., down to the level of Hospital Referral Regions (defined as a regional health care market, which may cross state boundaries, of which there are 306 in the U.S.).  There is ongoing debate as to the relative contributions of race, gender, poverty, education level and place to these variations. The Office of Epidemiology of the Maternal and Child Health Bureau recommends using an analytic approach (Fixed Effects or hybrid Fixed Effects) to research on health disparities to reduce the confounding effects of neighborhood (geographic) variables on the outcomes. 
The importance of family planning programs
Family planning programs (including contraceptives, sexuality education, and promotion of safe sex) play a major role in population health. Family planning is one of the most highly cost-effective interventions in medicine. Family planning saves lives and money by reducing unintended pregnancy and the transmission of sexually transmitted infections.
For example, the United States Agency for International Development lists as benefits of its international family planning program:
- "Protecting the health of women by reducing high-risk pregnancies"
- "Protecting the health of children by allowing sufficient time between pregnancies"
- "Fighting HIV/AIDS through providing information, counseling, and access to male and female condoms"
- "Reducing abortions"
- "Supporting women's rights and opportunities for education, employment, and full participation in society"
- "Protecting the environment by stabilizing population growth"
Population health management (PHM)
One method to improve population health is population health management (PHM), which has been defined as “the technical field of endeavor which utilizes a variety of individual, organizational and cultural interventions to help improve the morbidity patterns (i.e., the illness and injury burden) and the health care use behavior of defined populations”. PHM is distinguished from disease management by including more chronic conditions and diseases, by use of "a single point of contact and coordination", and by "predictive modeling across multiple clinical conditions". PHM is considered broader than disease management in that it also includes "intensive care management for individuals at the highest level of risk" and "personal health management... for those at lower levels of predicted health risk". Many PHM-related articles are published in Population Health Management, the official journal of DMAA: The Care Continuum Alliance.
- Community health
- Economic inequality
- Health disparities
- Health Impact Assessment
- Inequality in disease
- List of countries by income equality
- Population Health Forum
- Social determinants of health
- Kindig D, Stoddart G. What is population health? American Journal of Public Health 2003 Mar;93(3):380–3. Retrieved 2008-10-12.
- http://www.healthypeople.gov/2020/topicsobjectives2020/overview.aspx?topicid=39 Social Determinants of Health overview tab
- Meeting Report of World Conference of Social Determinants of Health held in Rio de Janeiro, Brazil, 2008 available at http://www.who.int/sdhconference/resources/Conference_Report.pdf
- McGinnis JM, Williams-Russo P, Knickman JR. 2002. The case for more active policy attention to health promotion. Health Affairs 21:78–93, also see National Academies Press free publication: The Future of Public Health in the 21st Century, available at http://www.nap.edu/catalog/10548.html
- Frankish, CJ et al. "Health Impact Assessment as a Tool for Population Health Promotion and Public Policy". Vancouver: Institute of Health Promotion Research, University of British Columbia, 1996. Retrieved 2008-10-12.
- World Health Organization. WHO definition of Health, Preamble to the Constitution of the World Health Organization as adopted by the International Health Conference, New York, 19–22 June 1946; signed on 22 July 1946 by the representatives of 61 States (Official Records of the World Health Organization, no. 2, p. 100) and entered into force on 7 April 1948. In Grad, Frank P. (2002). "The Preamble of the Constitution of the World Health Organization". Bulletin of the World Health Organization 80 (12): 982.
- World Health Organization. 2006. Constitution of the World Health Organization – Basic Documents, Forty-fifth edition, Supplement, October 2006.
- Health People 2020 found at http://www.healthypeople.gov/2020/default.aspx
- Chandra, A; Skinner, JS (2004). Geography and Racial Health Disparities, Chapter 16 of Critical Perspectives on Racial and Ethnic Differences in Health in Late Life. National Research Council.
- http://www.dartmouthatlas.org/data/region/%7C Data by Region, the Dartmouth Atlas of Health Care|access date=November 16, 2013
- Schempf, AH, Kaufman, JS (2012). "Accounting for context in studies of health inequalities: a review and comparison of analytic approaches.". Annals of Epidemiology 10. doi:10.1016/j.annepidem.2012.06.105.
- Tsui AO, McDonald-Mosley R, Burke AE (April 2010). "Family planning and the burden of unintended pregnancies". Epidemiol Rev 32 (1): 152–74. doi:10.1093/epirev/mxq012. PMC 3115338. PMID 20570955. "International studies confirm that family planning is among the most cost-effective of all health interventions (80, 81). The cost savings stem from a reduction in unintended pregnancy, as well as a reduction in transmission of sexually transmitted infections, including HIV."
- USAID. Family planning. Retrieved 2008-10-12.
- Hillman, Michael. Testimony before the Subcommittee on Health of the House Committee on Ways and Means, hearing on promoting disease management in Medicare. 2002-04-16. Retrieved 2008-10-12.
- Howe, Rufus, and Christopher Spence. Population health management: Healthways' PopWorks. HCT Project 2004-07-17, volume 2, chapter 5, pages 291-297. Retrieved 2008-10-12.
- Coughlin JF, Pope J, Leedle BR. Old age, new technology, and future innovations in disease management and home health care. Home Health Care Management & Practice 2006 Apr;18(3):196-207. Retrieved 2009-01-09.
- DMAA: The Care Continuum Alliance. Publications. Population Health Management. Retrieved 2008-10-12.
- Lopez AD, Mathers CD, Ezzati M, Jamison DT, Murray CJ (May 27, 2006). "Global and regional burden of disease and risk factors, 2001: systematic analysis of population health data". The Lancet 367 (9524): 1747–1757. doi:10.1016/S0140-6736(06)68770-9. PMID 16731270.
- Institute for Population Health Improvement at the University of California-Davis Health System
- New York University Department of Population Health
- Population Health Institute at the University of Wisconsin–Madison
- Canadian Institute for Health Information
- Institute of Population Health at the University of Ottawa, Canada
- Population and Health Graduate Program in the Dept. of Population and Family Health Sciences at the Johns Hopkins Bloomberg School of Public Health
- Population Health Forum website
- A Population-Based Risk Management Framework for Cancer Control
- Public Health Agency of Canada's take on population health
- Canadian Policy Research Secretariate report on population health
- Private Sector Partnerships for Better Health