Explaining the Rise in Educational Gradients in Mortality

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The mortality gap between males with and without a college degree rose 21 percentage points during [the 1971-2000 period].

The long-standing inverse relationship between education and mortality strengthened substantially late in the twentieth century. In 2000, college-educated 25-year olds could expect to live seven years longer than their peers with less schooling. In Explaining the Rise in Educational Gradients in Mortality (NBER Working Paper No. 15678), co-authors David Cutler, Fabian Lange, Ellen Meara, Seth Richard, and Christopher Ruhm investigate the extent to which behavioral risk factors, such as smoking and obesity, may explain how and why education-related disparities in mortality rates changed between the early 1970s and the end of the twentieth century.

The authors report several important facts about recent mortality trends. First, even after one controls for smoking and body weight, the college-educated have lower expected mortality rates than their less educated peers. This differential increased from 12 percent to 25 percent for men and from 9 percent to 20 percent for women between 1971 and 2000. Second, current smoking is associated with a much larger increase in mortality rates than other risk factors, and the adverse effects of smoking on mortality may have actually increased over time. Severe obesity raises mortality risk, too.

Third, although higher levels of mortality among the less educated are due in part to higher rates of smoking and obesity, the trends in smoking and obesity explain little if any of the relative increase in mortality for the less educated over the last three decades. The mortality gap between males with and without a college degree rose 21 percentage points during that time, while the authors estimate that differential changes in smoking and obesity would have led to a 4 or 5 point decrease. For women, patterns of smoking and obesity only can explain approximately 3 points out of the 42 percentage point increase.

Finally, the authors examine deaths from cardiovascular diseases (CVD) and cancer, the two most important sources of mortality in the United States. Both sources of mortality are influenced by behavioral risks such as smoking and obesity. The authors find that changes in cancer mortality play a key role in explaining the trends in the educational gradients in total mortality, but they find little evidence that changing risk profiles explain the widening in the education mortality gradient. Instead, changing returns to education and to various behavioral risk factors have favored the more educated. Thus, it is the return to education, conditional on health behaviors, that is important. The mortality returns to risk factors and, conditional on risk factors, the return to education, have grown over time for reasons that are not yet understood.

There are several possible explanations for these findings. One is that the highly educated have better access to medical care and better adherence rates to prescribed regimes. Another is that environmental and geographically-based risks may have declined more over time for the highly educated. But these results do not imply that improvements in the health-related lifestyles of the less educated would yield no benefits - they suggest that reducing smoking, obesity, hypertension, and elevated cholesterol should have resulted in reduced mortality. However, the results suggest that even the complete elimination of disparities in behavioral risks across education groups would be unlikely to do away with education-differentials in mortality.

-- Claire Brunel