Social class differences in coronary heart disease in middle-aged British men: implications for prevention.

BACKGROUND Though social class differences in coronary heart disease (CHD) are well recognized, few studies have assessed the effect of imprecision in social class assessment on the relationship or the overall contribution of social class to attributable CHD risk. METHODS Prospective observational study of the relationship between occupational social class (assessed at baseline and after 20 years), major CHD (coronary death and non-fatal myocardial infarction) and all-cause mortality rates over 20 years among 5628 middle-aged British men with no previous evidence of CHD. RESULTS The age-adjusted hazard of major CHD for manual men relative to non-manual men was 1.41 (95% CI: 1.21, 1.64) before correction and 1.50 (95% CI: 1.25, 1.79) after correction for imprecision of social class measurement. The imprecision-corrected estimate was attenuated to 1.28 (95% CI: 1.06, 1.54) after adjustment for the adult coronary risk factors (blood cholesterol, blood pressure, body mass index, cigarette smoking, alcohol, physical activity, and lung function) and to 1.20 (95% CI: 0.99, 1.45) following further adjustment for height. The population attributable risk fraction of major CHD for social class (manual versus non-manual) was 22% after correction for imprecision in social class, which was reduced to 14% after adjustment for the adult coronary risk factors, and 10% after further adjustment for height. Similar results were obtained for all-cause mortality. CONCLUSIONS Even taking account of measurement imprecision, the contribution of social class to overall CHD risk is modest. Population-wide strategies to reduce major CHD risk factors are likely to have greater potential benefits for CHD prevention than strategies designed specifically to reduce social inequalities in CHD.