In Part I of this report, the panel reviewed the available evidence regarding cross-national differences in health and concluded that the United States has experienced dramatic improvements in health over the past century but still appears to have a major health disadvantage compared with other high-income countries. The research literature shows that this disadvantage has actually existed for many decades and appears to be growing, especially for women. On almost every measure of life expectancy, the United States ranks at or near the bottom compared to other high-income countries. Each year, other high-income countries are improving their health at a much faster rate than the United States, and the United States currently ranks lowest on a variety of health measures.
The evidence reviewed in Part I also makes clear that this disadvantage is pervasive: the United States ranks at or near the bottom on multiple measures of mortality and morbidity, in all age groups up to age 75, in males and females alike, and in virtually all other subgroups of the population. Furthermore, the disadvantage does not appear to be simply a reflection of lower levels of health among Americans who are uninsured and/or poor, as important as these are. Even advantaged Americans seem to be less healthy than their peers in other high-income countries. This pervasiveness also suggests the need to not only look at specific health conditions such as heart disease or other causes of morbidity and mortality, such as injuries, but also to pursue overarching, multisystemic explanatory factors at play. It is these potential explanations that are the focus of this second part of the report.
Our approach to this task was informed by our charge, which was to “propose alternative explanations or potential causes of the reported health
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
provides a concise summary of this evidence and refers readers to comprehensive research reviews and landmark studies.
The chapters that follow focus instead on the second and third questions. For example, the second question entails not only demonstrating whether particular risk factors are more common in the United States than elsewhere, but also whether they have different effects on health outcomes. Countries with the same levels of hypertension (in untreated populations) or the same levels of poverty may experience different health outcomes if, respectively, one country performs better in controlling blood pressure or has a stronger safety net to help poor people avoid health complications. Although we did not systematically examine these differential effects, we did consider them when we knew there was some evidence available. For example, Chapter 6 reviews evidence that the lack of a college degree may have greater health consequences in the United States than elsewhere.
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