ABO blood group and cardiovacular disease: the Framingham study.

Following determination of ABO blood type at the sixth biennial examination, the Framingham Heart Study cohort was followed for the occurrence of cardiovascular events for a period of 10 years. A significant association was found between blood type and intermittent claudication, with blood group O showing the lowest rates. Slight but non-significant excesses for certain other CHD events were also found in non-O individuals. Serum cholesterol showed marginally significant but consistent elevations in non-O subjects but the increased risk in non-O individuals was found to occur independently of the known intermittent claudication risk factors. Since the observed relationship between blood type and intermittent claudication occurs independently of the usual atherosclerotic risk factors, blood type, possibily through an effect on clotting, should be considered in the pathogenesis of intermittent claudication.