What Does Population Health Mean?

The practice of medicine enables us to live long and healthy lives, but it cannot be the primary source of good health

Virtually no one takes the idea of addressing the non-medical determinants of health seriously enough.

The central message of research in population health, beginning in earnest with the work of the British physician-demographer Thomas McKeown, has been dramatic: Medical interventions, from primary care to chronic treatment, explain only a minority of the improvement in lifespan and well-being that populations in the world’s richest countries have experienced since industrialization.

This includes the significant achievements of public health work, especially life-saving measures like vaccinations.

Few of us would prefer to live in a world that denies us the advantages of public health and disease prevention, but these activities are not the primary reason why our health has improved and our lives have lengthened compared to 200 years ago.

Instead, nutrition was the main factor underlying improved health over the industrial-era demographic transition, occurring roughly between 1800 and 1940 in the United States. This transition meant that, for the first time since the era of hunter-gatherers, most ordinary people had enough to eat and sufficient quantities of essential nutrients. (The United States, with its vast and largely untapped natural wealth, was a relatively well-fed country even before industrialization, but measures of caloric intake and hunger tend to under-represent improvements in diet quality.)

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Demographic changes secured this gain, as instead of using this agricultural surplus to raise more children, people in industrialized, urbanized countries eventually chose to have fewer of them. By comparison, primary care and hospitals had smaller effects on length of life and overall well-being, and were barely available to most people until decades after the bulk of this demographic transition had taken place.

Notably, most of the importance of improved medical care as reflected in health outcomes comes from a single sub-field: reproductive health. Childbirth has been a leading cause of death for women for the whole of human history and in every kind of society, with historical rates of both maternal and infant mortality around 100 times higher than those measured in wealthy countries today.

In addition to nutrition, other non-medical influences on health include the built environment, social connectedness, and cultural practices. These factors shape human health through the foods that we choose to eat (and how we choose to eat them), the kind of physical activity that is in our routine, the risky activities in which we indulge, and the relationships on which we build our lives.


So, what does a healthy person tend to look like?

  • This person might follow any of a variety of diets, but probably eats less food than most of us do.
  • This person is a non-smoker and does not drink alcohol heavily or in binges.
  • This person has active hobbies and avoids drugs – including most legal ones – and wastes little time on hobbies that are dangerous or lacking in nourishment for either the body, mind, or soul.
  • This person walks frequently, both as a matter of functioning and as a matter of fun.
  • This person has a clear sense of purpose in life, a firm sense of place in his or her community, and a strong network of close, supportive relationships in addition to a wider network of weaker but still friendly relationships.
  • Finally, this person probably spends more time either reading or socializing and negligible time watching television or playing video games compared to most of us.

It should be more or less obvious from this description why encouraging these changes is so difficult. The conditions and behaviors that enable good health are cumulative and interrelated. They assume a great deal about a person’s agency and capabilities. How many of us choose the community into which we are born, the habits ingrained by our upbringing, or the values instilled in us about what it means to live a good life?

Non-medical influences on health are least effective at improving health outcomes when addressed piecemeal. Interventions need to be complete to have a sustained and positive effect. For example, making cheap and healthful foods available to more people is unlikely to help someone who does not know how to prepare them or who lacks access to a kitchen, to say nothing of someone who does not really believe that improving their eating habits is worthwhile in the first place.

Population health cannot only comprise interventions targeted toward the margins, like 500 healthful meals served at the local kitchen or 2,000 miles walked by local employees of the ABC International Chemical Conglomerate during its spring fitness challenge.

Its lessons are greater in scope, to the point that it becomes difficult to read the relevant literature without getting the sense that an entire way of life is up for indictment. And this way of life is not limited to only the poorest or most marginal people in the United States and other wealthy countries, although a disproportionate share of its burden falls on the least of these.

This is the challenge of population health: Where do we begin? How can we persuade ourselves to make such fundamental changes — both individually and collectively — for the sake of our health and well-being?

One of the most encouraging starting points is that, regardless of our religious commitments or ethnic backgrounds, many of these values and practices have been with us for a long time. But, to varying degrees, we have lost our grip on them, or we fail to take them seriously, or we fail to understand them.

population health
In an industrialized, urbanized world, physical exercise and other ingredients for a healthy life have become less ingrained into our daily lives. How often do you take the stairs instead of the elevator?

Many of them have become so de-contextualized from our day-to-day existence that they might seem irrelevant or impractical in guiding us toward a better life, especially in our urbanized, industrialized, and commodified society where mass media is the dominant authority and consumerism serves as the leading source of shared values.

Another relevant lesson is the limits of clinical medicine. All of us are better off with access to health care, but we should understand the limits of what it can achieve and what we ought to ask of it.

Clinicians can do a great deal, but there is much that they cannot do. A doctor cannot move an obese person’s home to a more walkable neighborhood, reduce the working hours of an adult who smokes to cope with the stress of holding several precarious part-time jobs, force a lonely person’s relatives to spend time visiting, or build a house free of mold for an asthmatic child.

Medicine provides essential support for living a long and healthy life, but it cannot be its source.

For most of us, hospitals and clinics are places through which we pass. We live our lives elsewhere — in our homes, neighborhoods, workplaces, schools, places of worship, bars, shops, restaurants, and so on. Whether our lives are long and healthy will reflect the character of these settings, what we do there, and how we relate to the people with whom we share them.

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