Smart people live longer

Earlier I discussed the evidence from Oscar winners that higher status leads to better health. Steve Sailer alerts me to a good article from Forbes challenging the status explanation in favor of an effect of IQ on health.

Why is it that, all around the world, those with more income, education and high-status jobs score higher on various measures of health? ....The traditional answer to these questions has been that greater wealth and social status mean greater access to medical care. But even ten years ago, when this magazine last delved into the topic (FORBES, Jan. 31, 1994), the available answers seemed inadequate. If access was the key, then one would have expected the health gap between upper and lower classes to shrink or disappear with the advent of programs like Britain's National Health Service and America's Medicare and Medicaid, not to mention employer-sponsored health insurance. In fact, the gap widened in both Britain and America as these programs took effect. The 1994 article cited a study of British civil servants--all with equal access to medical care and other social services, and all working in similar physical environments--showing that even within this homogeneous group the higher-status employees were healthier: "Each civil service rank outlived the one immediately below." How could this be?

Today the standard answer--or, at least, the answer you are guaranteed to get from the WHO and other large health bureaucracies--is that inequality itself is the killer. ...

[But a new theory has been put forward by] Linda Gottfredson, a sociologist based at the University of Delaware, and psychologist Ian Deary of the University of Edinburgh. Their solution to the age-old mystery of health and status is at once utterly original and supremely obvious. The rich live longer, they write, mainly because the rich are smarter. The argument rests on several different propositions, all well documented. The crucial points are that (a) social status correlates strongly and positively with IQ and other measures of intelligence;(b) intelligence correlates strongly with "health literacy," the ability to understand and follow a prescription for disease prevention and treatment; and (c) intelligence is also correlated with forward planning--which means avoidance of health risks (including smoking) as they are identified.

The first leg of that argument has been established for many decades. In modern developed countries IQ correlates about 0.5 with measures of income and social status--a figure telling us that IQ is not everything but also making plain that it powerfully influences where people end up in life. The mean IQ of Americans in the Census Bureau's "professional and technical" category is 111. The mean for unskilled laborers is 89. An American whose IQ is in the range between 76 and 90 (i.e., well below average) is eight times as likely to be living in poverty as someone whose IQ is over 125.

Second leg: Intelligent people tend to be the most knowledgeable about health-related issues. Health literacy matters more than it used to. In the past big gains in health and longevity were associated with improvements in public sanitation, immunization and other initiatives not requiring decisions by ordinary citizens. But today the major threats to health are chronic diseases--which, inescapably, require patients to participate in the treatment, which means in turn that they need to understand what's going on....

Deary was coauthor of a 2003 study in which childhood IQs in Scotland were related to adult health outcomes. A central finding: Mortality rates were 17% higher for each 15-point falloff in IQ. One reason for the failure of broad-based access to reduce the health gap is that low-IQ patients use their access inefficiently. A Gottfredson paper in the January 2004 issue of the Journal of Personality & Social Psychology cites a 1993 study indicating that more than half of the 1.8 billion prescriptions issued annually in the U.S. are taken incorrectly. The same study reported that 10% of all hospitalizations resulted from patients' inability to manage their drug therapy. A 1998 study reported that almost 30% of patients were taking medications in ways that seriously threatened their health. Noncompliance with doctors' orders is demonstrably rampant in low-income clinics, reaching 60% in one cited s tudy. Noncompliance is often taken to signify a lack of patient motivation, but it often clearly reflects a simple failure to understand directions.

Although I doubt that IQ explains the longevity of Oscar winners relative to nominees I think it does explain a great deal - indeed, it would be astonishing if IQ didn't impact health. By the way, I recommend Deary's Intelligence: A Very Short Introduction and here is an even shorter introduction.