Last month we began coupling this column with invited editorials from experts to help frame and operationalize a Public Health of Consequence. The first of these editorials introduced the concept of Population Health Science as a discipline unto its own.1 The notion of Population Health Science as a discipline aims to inform how we approach our work in public health, restate how we frame our hypotheses, and help forge a new understanding of the determinants of population health to effectively improve the health of populations. This month’s editorial by Krieger helps focus how we approach our work through the lens of theory.2 Krieger asks us to stand at theory-informed crossroads and critically examine our work against five main axes. Krieger makes a powerful argument that theory stands at the crossroads of imagination, observation, metaphor, insight, and action—key elements of a public health of consequence. These axes we would argue build well on the themes of a population health science that
is the study of the conditions that shape distributions of health within and across populations, and of the mechanisms through which these conditions manifest as the health of individuals.1(p633)
In much the same way as population health science can be framed as a way of thinking, a theoretical framing can help ground our questions—and our perspectives to make sure that we ask high-priority questions—toward a public health of consequence.
Building on these two editorials, we comment here on two articles in this issue of AJPH that address a core problem of latter day public health concern—obesity—and in so doing illuminate one of the core principles of population health science, as well as the theory that can inform our practice.
Chen et al.3 tackle obesity, one of the sentinel domestic and increasingly most pressing global challenges to population health. Chen et al. show that neighborhood food environment is associated with both obesity and overweight status, even when taking into account home food environment. This analysis echoes both invited editorials. First this analysis well demonstrates that “ubiquitous causes can exert a powerful impact on disease incidence.”1(593) Neighborhood food environment is the quintessential “ubiquitous cause,” an exposure that affects how residents of the neighborhood behave and the food they eat. It is an inescapable, hence ubiquitous, determinant of dietary patterns, and a foundational driver of population health. Second, this work finds itself, in Krieger’s2 terminology, at the crossroads of science and society, showing us that societal factors stand to produce health above and beyond an individual and her family.
Importantly, the work by Chen et al.,3 reinforces the importance for a public health of consequence, to ask the right question to tackle the problem at hand. Namely, obesity in the United States has risen dramatically in the past 30 years.4 It defies plausibility that our eating behavior has changed that much during this short time period, or that any constitutional or genetic factors have changed sufficiently to contribute to rising obesity. This then suggests that a focus on solving the obesity problem must indeed lie in examining the social and cultural factors that have plausibly changed dramatically over just a few decades and that must be tackled to address the obesity challenge. The work by Chen et al.3 illustrates some such factors but perhaps most importantly points us away from individual-based solutions to a problem whose roots clearly cannot be based solely at the individual-level but must lie at the crossroads of science and society.
A similar message emerges from the work of Wasfi et al.,5 also in this issue of AJPH, illustrating the role of neighborhood walkability, and also echoing the work of previous authors who have shown that structural factors (not individual factors), like neighborhood walkability, are core determinants of individual walking behavior.6 We also applaud both authors for pairing appropriately sophisticated (but often impenetrable) tables of regression coefficients with clear and refreshingly simple graphics that give the take home message at a glance. The importance of this cannot be overstated. We can only create a public health of consequence if important findings can be communicated and understood. The table–figure juxtaposition is illustrated well by Wasfi et al.5—which is easier to digest: the unweighted random coefficient estimate of 0.45 in Table 2 or the green line in Figure 2 of their article? We would argue it is the latter.
As we note that these two articles build well on the two editorials accompanying this section, we conclude by bringing to the reader’s attention that previous work published nearly two decades ago in AJPH had highlighted some of the core concepts being discussed here well.7 Schwartz and Carpenter coined the term “the right answer for the wrong question,” suggesting that looking, for example, for an individual-based solution to a problem like obesity that clearly must have societal roots may usefully be called a type III error. By way of illustration, the obesity epidemic in the United States over the past few decades has coincided with an enormous increase in research about the genetics of obesity. While this approach may yield important mechanistic insights into how we gain weight, it most decidedly will not tell us anything about why obesity has increased over the past few decades, unless we were to argue that our genes have dramatically mutated over the past 30 years. This, therefore, represents a type III error and is work that is neither particularly consequential for public health, informative for population health science, nor suitably at the crossroads of society and health where much of the solution for this particular problem must dwell. Type III error has not really caught on in public health, but we posit that it unfortunately applies to far too many approaches we often blindly adopt uncritically in public health. Ubiquity as central to population health science1 and the crossroads of society and health as an animating theory as articulated by Krieger2 are two additions to our thinking that can, with some luck, steer us in a better direction, toward a public health of consequence.
REFERENCES
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