Genetic and environmental influences on waist-to-hip ratio and waist circumference in an older Swedish twin population.

Abstract

To investigate the genetic and environmental influences on waist-to-hip ratio (WHR) and waist circumference (WC) measurements in males and females. Measurements taken from 1989-1991 as part of The Swedish Adoption/Twin Study of Aging (SATSA) were used for analysis. The SATSA sample contains both twins reared together as well as twins reared apart. 322 pairs of twins (50 identical, 82 fraternal male pairs and 67 identical, 123 fraternal female pairs); age range: 45-85y (average age, 65y). Waist-to-hip ratio (WHR), waist circumference (WC) and body mass index (BMI). In males, additive genetic effects were found to account for 28% of the variance in WHR and 46% of the variance in WC. In females, additive genetic effects were found to account for 48% of the variance in WHR and 66% of the variance in WC. The remaining variance in males was attributed to unique environmental effects (WHR, 72%; WC, 54%) and in females the remaining variance was attributed to unique environmental effects (WHR, 46%; WC, 34%) and age (WHR, 6%). When BMI was added into these models it accounted for a portion of the genetic and environmental variance in WHR, and over half of the genetic and environmental variance in WC. There are both genetic and environmental influences on WHR and WC, independent of BMI in both males and females, and the differences between the sexes are significantly different.