Population health is defined as “the health outcomes of a group of individuals, including the distribution of such outcomes within the group”. (http://ajph.aphapublications.org/doi/abs/10.2105/AJPH.93.3.380) These groups are often geographic populations such as nations or communities, but can also be other groups such as employees, ethnic groups, disabled persons, prisoners, or any other defined group. The health outcomes of such groups are of relevance to policy makers in both the public and private sectors.
Note that population health is not just the overall health of a population but also includes the distribution of health. Overall health could be quite high if the majority of the population is relatively healthy—even though a minority of the population is much less healthy. Ideally such differences would be eliminated or at least substantially reduced.
Healthy People 2020 says, “Positive changes in individual behavior can reduce the rates of chronic disease in this country. (Source: http://www.healthypeople.gov/2020/about/foundation-health-measures/Determinants-of-Health)
The Association of Faculties of Medicine of Canada (AFMC) says in their Primer on Population Health, A virtual textbook on Public Health concepts for clinicians (http://phprimer.afmc.ca/Part1-TheoryThinkingAboutHealth/Chapter2DeterminantsOfHealthAndHealthInequities/HealthBehaviours):
Many of the underlying health determinants influence health via personal behaviours. For example, a lack of exercise, high-fat diet, and alcohol or tobacco consumption form personal risk factors for disease, whereas regular activity and a healthy diet confer health benefits.
Clinicians generally find that altering patients’ health behaviour (helping them to stop smoking, take up exercise, etc.) is slow and difficult. Psychology offers several theoretical models that identify the personal and situational factors likely to influence health behaviour; these help explain why behaviour is often so hard to change.
POPULATION HEALTH vs. INDIVIDUAL HEALTH
Population health and individual health are intertwined. The same external factors (see the infographic above) affect both. To effectively improve the health in a community, both aspects need to be considered.
Onyebuchi A. Arah says in an article (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2698967/):
The relationship between individual and population health is partially built on the broad dichotomization of medicine into clinical medicine and public health. Potential drawbacks of current views include seeing both individual and population health as absolute and independent concepts. I will argue that the relationship between individual and population health is largely relative and dynamic. Their interrelated dynamism derives from a causally defined life course perspective on health determination starting from an individual’s conception through growth, development and participation in the collective till death, all seen within the context of an adaptive society. Indeed, it will become clear that neither individual nor population health is identifiable or even definable without informative contextualization within the other. For instance, a person’s health cannot be seen in isolation but must be placed in the rich contextual web such as the socioeconomic circumstances and other health determinants of where they were conceived, born, bred, and how they shaped and were shaped by their environment and communities, especially given the prevailing population health exposures over their lifetime. We cannot discuss the “what” and “how much” of individual and population health until we know the cumulative trajectories of both, using appropriate causal language.