What causes heart disease? (Socioeconomic status edition)

Seth Roberts, of Shangri-La Diet fame, advocates, or is at least open to, the idea that whether a diet is low fat, high fat, or in between, and no matter what one's serum cholesterol level is, there's absolutely no effect one way or another on the chances of developing coronary artery disease. In a recent post, he mentions a couple of ideas bearing on this: one is Malcolm Kendrick's notion about serum cholesterol levels and lack of correlation to heart disease; the other is the social gradient in health.

The social gradient says that those higher on the social hierarchy, other things being equal, have better health than those lower. Naturally, many on the left ascribe the difference to anxiety or stress, the idea apparently being that if you're lower on the social scale, you worry about your position, and this somehow brings on heart disease.

The best explanation for this phenomenon is, in my opinion, Linda Gottfredson's Intelligence: Is It the Epidemiologists’ Elusive “Fundamental Cause” of Social Class Inequalities in Health?:

Virtually all indicators of physical health and mental competence favor persons of higher socioeconomic status (SES). Conventional theories in the social sciences assume that the material disadvantages of lower SES are primarily responsible for these inequalities, either directly or by inducing psychosocial harm. These theories cannot explain, however, why the relation between SES and health outcomes (knowledge, behavior, morbidity, and mortality) is not only remarkably general across time, place, disease, and kind of health system but also so finely graded up the entire SES continuum. Epidemiologists have therefore posited, but not yet identified, a more general “fundamental cause” of health inequalities. This article concatenates various bodies of evidence to demonstrate that differences in general intelligence (g) may be that fundamental cause.

IQ is important for life outcomes, whether they're as varied as income, ability to avoid accidents, doing well in school, or health. Those higher in socioeconomic status (SES) have risen higher because of higher intelligence; their higher IQs mean that they also have better health and less heart disease.