Magnified risks from cigarette smoking for coronary prone families in Utah.

The contribution of currently accepted risk factors to the familiality of early coronary heart disease (CHD) is poorly understood. In a telephone and mail survey, risk factor and disease morbidity and mortality data were collected from 100 proband and 185 control families encompassing about 40,000 person-years of experience. Probands were white married men who had died of CHD by age 45. There was a threefold increase in CHD incidence among first-degree relatives of probands compared with control families. In all, 67% of probands had at least one first-degree relative with early CHD, and 29% had two or more first-degree relatives with early CHD compared with 8% of the control families with two or more cases of early CHD. The most striking new finding of this study is the apparently magnified liability of cigarette smoking in families prone to have early coronary heart disease. This effect was seen strongly at younger ages (under 50). Furthermore, in about a third of all families with a history of early CHD, smoking seemed to be the only risk factor contributing to the familial occurrence of the disease. The findings show a large excess absolute risk for CHD among smoking members of proband families and further suggest a possibly heritable susceptibility to the deleterious effects of smoking in many families prone to early coronary disease. Modification of coronary risk factors, especially cigarette smoking, would be of greatest benefit among members of high-risk families.