Is income or education a predictor of risk for coronary heart disease? British medical researchers set out to answer this question by measuring one of the subclinical signs of heart disease: the extent of coronary artery calcification in men and women in their 30s.

Using a randomly selected sample of 149 men and women, none of whom had a history of coronary heart disease, and measuring the amount of plaque in their blood vessels using electron beam computed tomography, the researchers found, after adjusting for various other factors (such as weight and blood pressure):

• Being in a manual occupation doubled the odds of having calcified arteries.

• Having left full time education before the age of 19 more than doubled the odds of having calcified arteries.

• Interestingly, adjustments for known risk factors for heart disease (including smoking) had little effect on the odds predicted by social class (occupation and education).

This indicates, say researchers, that "the biological mechanisms through which social inequalities affect risk for coronary heart disease have yet to be discovered."

Source: Helen M Colhoun, "Cross sectional study of differences in coronary artery calcification by socioeconomic status," British Medical Journal, November 18, 2000.

For text http://bmj.com/cgi/content/full/321/7271/1262