Aggregation of plasma lipids and lipoproteins in families with and without coronary heart disease

Familial aggregation of total plasma cholesterol (TC), triglyceride (TG), low density lipoprotein cholesterol (LDL-C) and high density lipoprotein cholesterol (HDL-C) was analyzed in 37 families with incidence cases of first myocardial infarction (MI), in 154 families of coronary heart disease (CHD) prevalence cases and in control families. Fasting plasma lipid levels were adjusted for age, sex, country of origin and season of year. Mean TC, LDL-C and TG levels were higher among cases, their spouses and among 17-year-old children of incidence cases than among control families. HDL-C was lower among cases and among wives of incidence cases than in their controls. No differences in HDL-C were noted among children. Mid parent-child correlations for TC and LDL-C were higher in 32 families of men who had a MI (r = 0.43 and r = 0.49) than for control families (r = 0.32 and r = 0.29, respectively). When the 5 families of mothers who had a first MI were included in the analysis, the case-child correlations for TC and LDL-C were 0.60 and 0.68, respectively. Father-child correlation for HDL-C was significantly lower (r = -0.17) among the MI incidence case families than among the control families (r = 0.22; P < 0.05). No substantial differences in familial correlations for lipid variables were noted in the CHD prevalence families and their controls. These findings suggest that total cholesterol and LDL-C levels, but not HDL-C levels, may be a risk marker in adolescents. The associations evident in adolescent children of families with MI incidence cases were not apparent in children whose parents had CHD on entering the study. This could be due to the probably greater misclassification of CHD prevalence cases than MI incidence cases, the awareness in patients with CHD and subsequent behavioural changes, to possible differences in patterns of survival in the two categories, or may reflect a chance finding.