disadvantage, going beyond previously tested explanations.” We began by adopting a social-ecological and life-course perspective to frame the question (Chapter 3), which led to our decision to systematically consider a broad range of factors that might influence individual- and population-level health: public health and medical care systems (Chapter 4), individual behaviors (Chapter 5), social factors, such as education and income (Chapter 6), environmental factors (Chapter 7), and policies and social values (Chapter 8).

Dividing these topics by chapter is an editorial device: the reality is that these influences are deeply interconnected. Rarely do these factors influence health in isolation, and a reductionist approach can miss interrelationships that affect health outcomes. For example, a U.S. health disadvantage with respect to diabetes might result partly from inadequate medical care (Chapter 4), but also from the obesity epidemic, a product of unhealthy diets and sedentary behavior (Chapter 5), and an obesogenic environment (Chapter 7). The latter disproportionately affects households that face financial stress (Chapter 6), because assistance programs to buffer the impact of this stress are limited (Chapter 8).

The editorial device of separating these topics into distinct chapters should therefore not obscure the complex, dynamic interrelationships between these factors and the different roles they play over the life course as health disadvantages evolve over time. While all of these disparate factors may play a role, it would be a mistake to assume that the topics in each chapter can be decomposed into independent risk categories that “add up” to the U.S. health disadvantage. The dynamic and synergistic interactions between causal factors, only some of which are fully understood, are central to the many issues we review in Part II.

Out of necessity, the panel was selective and systematic in its approach to these complex and comingled influences. In each of the chapters in Part II, the panel focused on three key questions to understand the U.S. health disadvantage:

1.   Does the set of factors matter to health?

2.   Does the set of factors have greater prevalence or health effects in the United States than in other high-income countries?

3.   Could this difference between the United States and other countries contribute to the U.S. health disadvantage?

Large bodies of research, at various stages of evolution and quality, have been devoted to the first question in this three-stage logical sequence and have been ably reviewed elsewhere. Rather than presenting this research in great detail, and because this was not the panel’s primary focus, the panel

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