Family history as an independent risk factor for ischaemic heart disease in a low incidence area (Galicia, Spain).

It has been suggested that a family history positive for coronary heart disease (CHD) increases the risk of CHD. We studied this association to determine the degree of risk, the independence of this association and the presence of interaction of a family history of CHD with the major known risk factors in a low incidence area. One hundred and six hospital cases (85 males and 21 females) of CHD and 106 hospital controls individually matched with each case for sex, age and place of residence (rural-urban) were studied. From every participant, information was collected on their personal and family history of cardiovascular disease and risk factors; height, weight, lipid profile and blood pressure were measured, and an electrocardiogram was recorded. Conditional logistic regression was used in the analysis. The observed odds ratio of patients suffering from CHD among those with, compared to those without, a positive family history of CHD was 4.95 (95% confidence interval = 1.27-19.28) after adjusting for the major known risk factors in each individual and their families (no interaction term remained in the model). The results support the hypothesis that a family history of CHD, acting through mechanisms other than known risk factors or their familial aggregation, is an independent risk factor for CHD even in a low incidence area. No interaction effect was observed between family history and the presence of the three major risk factors of CHD. This should help to identify individuals at greater risk of CHD.