IQ may help explain disparities in heart disease

NEW YORK (Reuters Health) - Differences in IQ may be one reason that lower-income individuals are more likely to die of heart disease than their more affluent counterparts, a study of U.S. men suggests.

It's well known that people with less education and lower incomes generally face higher risks of a range of diseases. Studies have pointed to many likely reasons -- including less access to healthcare and other resources, poorer living conditions, chronic stress and higher rates of lifestyle risk factors, like smoking and physical inactivity.

However, those factors do not seem to fully explain the disparities.

In the new study, published in the European Heart Journal, researchers looked at the relationship between IQ and the risk of dying from heart disease or stroke among nearly 4,300 male U.S. veterans.

All of the men were given intelligence tests when they entered the Army during the Vietnam War, then were tested again in middle age. Over the following 15 years, 62 study participants died of heart disease.

In general, the study found, men of the lowest socioeconomic status -- measured by income, occupation and education -- were between two and seven times more likely to die of causes related to heart disease than the most advantaged men.

"Classical" risk factors, including high blood pressure, smoking and obesity, explained about 40 percent of the disparity, according to the researchers. But IQ itself also appeared to play a role, explaining another quarter of the socioeconomic gap.

It's not clear whether directly IQ, per se, affects heart disease risk, the researchers say.

IQ may essentially serve as an "index of environmental 'insults' accumulated across the lifetime," including illnesses, chronic stress and unhealthy lifestyle habits, explained lead researcher Dr. David Batty, of the Medical Research Council's Social and Public Health Sciences Unit at the University of Glasgow.

This idea, he told Reuters Health, is supported by the finding that IQ during middle age was more strongly connected to cardiovascular risks than IQ in young adulthood was.

Still, if IQ does contribute to heart disease and stroke, there are practical implications, the researchers say.

Simplifying prevention messages -- whether it is a doctor talking to a patient, or a health campaign aimed at the general public -- may help reach more people, according to Batty.

As an example, he pointed to the complex and sometimes confusing messages about dietary fats, some of which are "good," some of which are "bad." Smoking is another case, Batty said; while most people probably know that quitting tobacco can only be good, the various strategies for quitting are not that well known or, for some people, easily accessed.

SOURCE: European Heart Journal, July 15, 2009.