Intrafamilial correlations of carotid intima-media thickness and flow-mediated dilation in a Siberian population

Background: Intima-media thickening and impaired endothelium-dependent vasodilation are complex phenotypes determined by genetic and environmental factors. Few studies assessed these phenotypes in the same subjects. The goal of our study was to assess the sex-specific intrafamilial aggregation of ultrasonographic carotid intimamedia thickness (IMT) and brachial flow-mediated vasodilation (FMD) in a Siberian population. Methods: We randomly recruited 81 nuclear families of Caucasian ancestry (129 parents and 157 offspring, mean age 52.4 and 26.3 years) in Novosibirsk, Russia. Carotid artery IMT and brachial artery FMD were assessed by ultrasound. Intraclass correlation coefficients were calculated between first-degree relatives and between unrelated spouse pairs for IMT and FMD in age-adjusted, sex-adjusted, and multivariate-adjusted models. Results: Multivariate-adjusted correlation coefficients in sib-sib pairs were 0.27 (P =.042) for INIT and 0.29 (P =.049) for FMD with heritabilities (h(2) = 2r) of 0.54 and 0.58, respectively. For IMT, the mother-offspring (r = 0.17, P = .051) and mother-daughter correlations (r = 0.28, P = .025) were significant, whereas the father-offspring correlation did not differ from zero (r = 0.11, P =.33). For FMD the father-offspring (r = 0.24, P = .042) and father-son correlations (r = 0.40, P =.051) were significant, whereas the mother-offspring correlation was only -0.09 (P =.39). The P value for the difference in familial aggregation of FMD between father-offspring and mother-offspring pairs was .018. Conclusions: Our findings confirm that a substantial proportion of the variability of carotid IMT and brachial FMD is attributable to genetic variation. They also suggest that offspring share more genetic or environmental determinants of FMD with fathers than their mothers.