Socioeconomic status, ABO phenotypes and risk of ischaemic heart disease: an 8-year follow-up in the Copenhagen Male Study

Objectives The association of socioeconomic status with the risk of ischaem ic heart disease is only partly explained by the uneven distribution of con ventional risk factors. We tested the hypothesis that an uneven socioeconom ic distribution of ABO phenotypes could contribute to the explanation. Design A prospective study controlling for age and other relevant potential confounders: smoking, physical activity, wine consumption, height, weight, serum lipids, blood pressure, hypertension, type II diabetes, serum seleni um concentration and soldering fumes exposure, Setting The Copenhagen Male Study, Denmark. Study participants Two thousand, nine hundred and ninety-three men aged 53- 74 years without overt ischaemic heart disease. Main outcome measure Incidence of ischaemic heart disease in an 8-year foll ow-up. Results Two hundred and forty-two men (8.1%) had a first ischaemic heart di sease event. There was no association between socioeconomic status and the ABO blood group phenotypes and, in accordance with this, ABO phenotype was not a confounder for the association of socioeconomic status with the risk of ischaemic heart disease. However, ABO blood group was a strong risk or e ffect modifier, Only among men with the O phenotype was socioeconomic statu s (social classes IV and V versus social classes I, II and III) associated with a significant excess risk (relative risk 1.7, 95% confidence interval 1.1 -2.7 and P = 0.02 after adjustment for confounders; the corresponding r elative risks among the A and B/AB phenotypes comparing low social classes with the higher social classes were 1.08 (P = 0.77) and 1.08 (P = 0.89), re spectively), Conclusion ABO phenotypes did not contribute directly to the explanation of socioeconomic inequalities in the risk of ischaemic heart disease, However , the finding of ABO phenotypes being effect modifiers for the association of socioeconomic status with the risk of ischaemic heart disease may open u p new possibilities of clarifying the roles of socioeconomic status and ABO blood group as cardiovascular disease risk factors. (C) 2000 Lippincott Wi lliams & Wilkins.