We don’t know why college educated people live longer

A good rule of thumb is that if David Cutler doesn’t know something about our health system nobody does. In his latest paper, coauthored by Fabian Lange, Ellen Meara, Seth Richards-Shubik, and Christopher J. Ruhm, Cutler tries to figure out why college educated Americans live longer than those with no college education. Actually, they try to figure out why the gap in life expectancy between the college educated and those who are not (the “education gradient”) is widening. The data only reveal a partial answer.

First note that we’re not talking trivialities here. In 2000, “college educated 25 year-olds could expect to live 7 years longer than their peers with less schooling.” In 2007 a 25 year old could expect to live to about age 80 (source, pdf). Presuming it was nearly the same in 2000, the life expectancy difference of college education is 9%.

The first question one should have is, “Is this causal?” That is, does college cause longer life? It could (why shouldn’t education matter for health and longevity?). Or it could not (so many other factors having nothing to do with education — like genes — should matter too). Probably it’s both. That’s still rather vague.

So, Cutler and colleagues tried to rule some things out. They succeeded at that, at least in part. Here are their main findings:

First, education gradients in mortality are stronger for men than women but have increased over time for both sexes. Second, despite the importance of smoking, obesity, hypertension, and cholesterol as determinants of population health, differential changes in these risk factors do not explain the widening educational gap in death rates since the 1970s. Finally, the mortality returns to risk factors and the return to education, conditioning on them, have grown over time for reasons that are not yet understood. Thus, even if less educated populations were able to achieve risk factor profiles mirroring those with more education, widening mortality differentials would likely persist. […]

In our main estimates, the mortality differential between males without and with college rose 22 percentage points [between 1971–1975 and 1987–2000], whereas corresponding trends in smoking and obesity predict a 4 point decrease, ceteris paribus For women, patterns of smoking and obesity explain approximately 3 points out of the 41 percentage point increase in the relative risk of death for the less educated. Risk factors play a more important role in some (but not all) alternative specifications but never explain more than a small fraction of the rising education-gradient in mortality.

Not being able to fully pin down the cause of the growing education gradient is bothersome.

[O]ur research highlights a fundamental puzzle in the literature on mortality and socioeconomic status. Our results do not imply that improvements in the health-related lifestyles of the less educated yield no benefits. To the contrary, reducing smoking, obesity, hypertension and high cholesterol would improve health. However, the results suggest that even the complete elimination of disparities in behavioral risks across education groups would be unlikely to substantially reduce education-related differentials in mortality.

But we can still speculate.

Three explanations seem likely to explain why the impacts of risk factors and education have increased over time. First, access to medical care may have become more important for detecting disease early and treating it appropriately, and the better educated have superior access to care. Second, the living environments (i.e. the exposure to environmental health risks) may have improved more over time for the better educated. Third, the management of chronic health problems may have become more sophisticated in ways that favor those with more schooling.

UPDATE: Yes, the authors examined the effect of income as well and it did not appreciably change the results reported in this post.

AF

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