GENETIC HERITABILITY AND COMMON ENVIRONMENTAL COMPONENTS OF RESTING AND STRESSED BLOOD PRESSURES, LIPIDS, AND BODY MASS INDEX IN UTAH PEDIGREES AND TWINS

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Abstract
The relative contributions of genes and shared environment to cardiovascular risk factors were studied in twins and pedigrees in 1983–1985. Sitting, standing, isometric hand grip, bicycling, and mentally stressed (serial subtraction) blood pressures were obtained from 146 male monozygous twins, 162 male dizygous twins, and 1,102 healthy adults in 67 Utah pedigrees. Fasting total plasma cholesterol, triglycerides, high density lipoprotein cholesterol (HDL), and body mass index were also measured. Heritability was estimated before and after adjusting for 12 environmental variables (measures of socioeconomic status; personality types; exercise levels; use of tobacco, alcohol, coffee, etc.) by using age-adjusted twin intraclass correlations. These heritabilities were compared with those obtained from a variance components analysis of the pedigree data separating genetic and common household effects. Sitting and standing blood pressure heritability estimates were much higher from twin than from pedigree data (39–63% in twins vs. 16–22% in pedigrees), as were those for cholesterol and triglycerides (65 and 75% from twins vs. 42 and 37% from pedigrees) and body mass index (51 vs. 21%). Estimates were similar for heritability of HDL cholesterol (51 vs. 45%). Most of the stressed blood pressure heritabilitles were similar to sitting blood pressure estimates. no common household effect (except for adjusted HDL cholesterol (24%), p <0.01) was statistically significant for the lipids, blood Pressures, or body mass index. Environmental variables correlated much better in monozygous twins and spouses than in dizygous twins, brothers, or sisters. Spouse correlations for lipids, blood pressures, and body mass index were low, with a maximum of 0.12 (p < 0.05) for HDL cholesterol. We conclude that genes contribute much more than shared environment to the well-recognized familial correlation of blood pressures, lipids, and body mass index.