Under a grant from the Robert Wood Johnson Foundation (RWJF), Altarum's Center for Sustainable Health Spending is studying the value of investments in nonclinical primary prevention; that is, interventions outside of the medical system (nonclinical) that reduce the incidence of illness or injury (primary prevention). What exactly are these interventions, and what are the mechanisms by which they reduce the incidence of health problems? Obvious examples would include such public health activities as safety regulations and promotion of healthy lifestyles, but, to identify the universe of such interventions, one must turn to the determinants of health. We introduce the concept of direct determinants of health to represent the mechanisms by which health is impacted by these interventions.
The Breadth of Nonclinical Primary Prevention
The determinants of health are commonly listed as genetics, health behaviors, social and physical environments, and medical care.[i] These five factors combine to produce individual and population health--any intervention designed to improve health must address one or more of them. Medical care interventions are, by definition, excluded from nonclinical primary prevention. Interventions involving the remaining determinants are, by definition, nonclinical. They typically improve health by reducing the occurrence of health problems (primary prevention).[ii] Thus, nonclinical primary prevention includes interventions into all of the determinants of health other than medical care.
Nonclinical primary prevention includes interventions into the social determinants of health (SDH), a subset of the determinants of health that have gained broad recognition and generated extensive research. Two definitions of SDH from the World Health Organization (WHO) are:
- ... the circumstances in which people are born, grow up, live, work and age, and the systems put in place to deal with illness. These circumstances are in turn shaped by a wider set of forces: economics, social policies, and politics.[iii]
- The complex, integrated, and overlapping social structures and economic systems that are responsible for most health inequities. These social structures and economic systems include the social environment, physical environment, health services, and structural and societal factors.[iv]
Among the circumstances included in SDH are education, income, occupation, social position, and the interaction of race, ethnicity, and gender with prevailing attitudes and practices. Interventions in any of these circumstances therefore contain elements of nonclinical primary prevention. For example, it has been argued that reducing class sizes in U.S. primary schools leads to improved health status and, therefore (somewhat counter intuitively), meets the literal definition of nonclinical primary prevention. The What Works for Health website contains many additional examples.
The broad scope of social determinants creates problems for a comprehensive study of nonclinical primary prevention. Is it simply too large to be addressable? Must it be artificially abridged in some way? In David Kindig's blog, "Population Health: If It's Everything, Is It Nothing?," he noted:
A look at the population health model ... suggests that indeed it is perhaps everything: a broad set of outcomes produced by a comprehensive set of determinants which are influenced or activated by programs and policies in the public and private sectors.
If nonclinical prevention approaches everything, will it become nothing in the sense of being conceptually intractable and unmanageable? Kindig offers a simple solution: Prioritize and focus on a smaller number of specific determinants that are known, a priori, to be important.
We follow this approach and suggest additional structuring of the determinants. There is a smaller set (which we call direct determinants) through which all others ("upstream" determinants) operate. The linkage of direct determinants and health is straightforward. The health impact of the upstream determinants flows through their linkage to the direct determinants. These two sets of linkages can be made more tractable by focusing, like Kindig, on factors known, a priori, to be most important.
Direct Determinants of Health
We define the direct determinants of health as those whose impact on health is readily apparent and which, taken together, fully explain variations in health. Upstream determinants affect health only through their impact on direct determinants. Direct determinants are close cousins to the "downstream" determinants of health discussed by Braveman, Egerter, and Williams,[v] and the "intermediate determinants" defined in the SDH conceptual framework developed by WHO.[vi]
Of the five determinants of health, we would call three direct: medical care, genetics, and health behaviors. Each has a clear pathway to health. But this is not a complete list. The remaining two determinants, social and physical environments, include both direct and upstream elements. We use the term environmental exposures to represent the direct elements and add it as a fourth direct determinant. It includes exposures to environmental toxins (air and water pollution, lead paint, asbestos), disease outbreaks, violent neighborhoods and relationships, and accident-prone surroundings; for example, poorly lit streets or unfenced swimming pools.
We add stress as a fifth direct determinant of health, since it is not represented in the other four determinants.[vii] Stress may be induced by concerns about such factors as finances, personal safety, job loss, divorce, and social standing. In an excellent survey of the literature, Peggy Thoits concludes that, "... differential exposure to stressful experiences is a primary way that gender, racial-ethnic, marital status, and social class inequalities in physical and mental health are produced."[viii]
The argument put forth above results in the following direct determinants of health:
- Medical Care
- Genetics
- Health Behaviors
- Environmental Exposures
- Stress
This list is a work in progress, and there may well be revisions in future iterations. For example, social cohesion is a key SDH element in the WHO framework and could be viewed as a sixth direct determinant. We currently treat it as an upstream determinant that affects health through its impact on direct determinants (e.g., by reducing stress, improving health behaviors, and perhaps helping to reduce environmental exposures). Should research reveal a strong, additional independent effect on health, we would include it as a direct determinant.
Our structure for the determinants of health (and of health disparities) is illustrated in the figure below. The upstream determinants affect health because of their effect on one or more of the direct determinants.[ix] The dashed arrow from the direct determinants to the upstream ones is intended to represent the complex feedback and other interactions among the determinants that are not shown explicitly in the figure. For example, education affects income, income affects access to care, and improved medical care can affect the ability to pursue education.
Social Determinants and Direct Determinants
Most SDH fall into our upstream determinants category. Consider the figure below, taken from Braveman et al., showing how the health status of children varies systematically with income. It also shows that white children tend to be in better health than Hispanic and black children even within the same income groups. The discovery of these variations is of great social significance. There are important additional insights to be gained through understanding the mechanisms by which income and race/ethnicity impact health. How much of these differences are attributable to differences in each of the direct determinants: genetics, medical care, health behaviors, environmental exposures, and stress?[x] What are the specific pathways through the direct determinants by which these upstream determinants affect health?
SDH are also implicated in the widening gap in health status between the United States and other developed countries, as documented by the Institute of Medicine. The IOM report states:
No single factor can fully explain the U.S. health disadvantage. It likely has multiple causes and involves some combination of inadequate health care, unhealthy behaviors, adverse economic and social conditions, and environmental factors, as well as public policies and social values that shape those conditions.
We believe it is critical to better understand the mechanisms by which the SDH contribute to this U.S. health disadvantage. Is life more stressful in the U.S.? If so, what social conditions are responsible? Are environmental exposures more prevalent? How important are differences in health behaviors and the amount and quality of medical care consumed?
If we are to reduce health disparities in the U.S. and shrink our health disadvantage vis-a-vis other developed countries, we will have to do a better job of primary prevention. Investments in SDH represent an underappreciated approach to this problem. And we believe that the concept of direct determinants of health can be used to highlight the value of such investments.
"Republished with permission of the Altarum Institute", http://www.altarum.org/