From the American College of Epidemiology
What matters most: quantifying an epidemiology of consequence

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Abstract

Risk factor epidemiology has contributed to substantial public health success. In this essay, we argue, however, that the focus on risk factor epidemiology has led epidemiology to ever increasing focus on the estimation of precise causal effects of exposures on an outcome at the expense of engagement with the broader causal architecture that produces population health. To conduct an epidemiology of consequence, a systematic effort is needed to engage our science in a critical reflection both about how well and under what conditions or assumptions we can assess causal effects and also on what will truly matter most for changing population health. Such an approach changes the priorities and values of the discipline and requires reorientation of how we structure the questions we ask and the methods we use, as well as how we teach epidemiology to our emerging scholars.

Section snippets

Our charge as epidemiologists and the limits of risk factor epidemiology

Individuals who are overweight might have longer life spans [1], [2] (or not [3]), blueberry and strawberry consumption may decrease risk for heart attacks [4] (or not [5]), moderate alcohol consumption is good for cardiovascular health [6] (or not [7]), green tea consumption might prevent stomach cancer [8] (or not [9]), and on and on. The list of diet, lifestyle, environmental, and genetic factors that purportedly cause or prevent a wide range of chronic diseases is voluminous, and often in

A re-emphasis on what matters most

The emphasis on identifying risk factors within a paradigm that hunts for precise causal effects obscures what we argue is the broader goal of the field—an attempt to identify “what matters most.” This approach urges us to identify what we can do about those factors that do indeed matter most for the health of populations, which necessarily involves both theory-driven approaches and a pragmatic assessment of what is likely to make a difference. Instrumentally, this would mean a focus on the

Mathematically understanding the effect of prevalent versus rare causes

The magnitude of the risk ratios and risk differences we obtain in our studies for the effect of an exposure on an outcome is dependent on the prevalence of those causes that interact with the exposure of interest [47], [39]. Thus, the idea that we can identify “the” causal effect of an exposure on an outcome is not only inefficient but also at odds with the very math of risk ratio and difference estimation when the exposure of interest is not sufficient to produce the outcome. We can clearly

From simulation to the community: shifting exposure prevalence across geographic space and time

One could potentially write off our previously mentioned example as a convenient mathematical exercise, but there is substantial empirical literature to indicate that such variations in the magnitudes of our effect estimates occur frequently in the empirical literature. These variations are sometimes explained by random chance [54], [55], faulty study design, or other methodologic bias, exposing our innate preference for exposures to have one true causal effect in the population.

Of course, the

Implications and conclusions for conducting an epidemiology of consequence

To conduct an epidemiology of consequence, we need to identify what matters most for population health so that we can guide public health stakeholders toward strategies that reduce the burden of these factors. It is hard to argue that we should not be thinking about what matters most as we endeavor to build our research questions and design studies to answer these questions, and our mathematical simulation demonstrates the importance of such an approach. The next question is, then, how do we

Acknowledgments

Funding was provided to Katherine Keyes by the National Institute on Alcohol Abuse and Alcoholism (K01AA021511).

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