Abstract 3903: Heritability of Carotid Intima-Media Thickness: A Twin Study
Background: Carotid intima-media thickness (IMT) is widely used as a surrogate marker for atherosclerosis. Heritability estimates of carotid IMT using family studies range between 0.24 and 0.92. However, no study has estimated heritability of carotid IMT using twins.
Methods: We conducted a classical twin study to estimate the heritability of carotid IMT. We selected 98 middle-aged male twin pairs (55 monozygotic [MZ] and 43 dizygotic [DZ]) from the Vietnam Era Twin Registry. All twins were free of overt cardiovascular disease. Carotid IMT was measured by ultrasound. Traditional cardiovascular risk factors were collected, including age, systolic blood pressure (SBP), diastolic blood pressure (DBP) and high-density lipoprotein (HDL). Regression analyses using generalized estimating equations (GEE) were used to determine the association of traditional cardiovascular risk factors with carotid IMT. Intraclass correlations and structural equation modeling were used to determine the relative contributions of genes and environment to the variation in carotid IMT.
Results: Age, systolic blood pressure (SBP), diastolic blood pressure (DBP) and high-density lipoprotein (HDL) were strongly associated with carotid IMT. In multivariable regression analysis, age, SBP and HDL remained significantly associated with carotid IMT. The intraclass twin correlations for carotid IMT were 0.66 (95% CI, 0.62–0.69) in MZ and 0.37 (95% CI, 0.29–0.44) in DZ twins, suggesting a genetic additive influence. After adjusting for traditional cardiovascular risk factors, the heritability of carotid IMT was 0.66 (95% CI, 0.48–0.78).
Conclusions: This classical twin study demonstrates that genetic factors account for a significant proportion of the variation in carotid IMT.