364 Sex Differences and Heritability of Two Indices of Heart Rate Dynamics: A Twin Study

Abstract

We investigated whether women show larger heart rate variability (HRV) than men after controlling for a large number of health-related covariates, using two indices of HRV, namely respiratory sinus arrhythmia (RSA) and approximate entropy (ApEn). In a twin design, the heritability of both indices was examined. The covariation between RSA and ApEn, a measure of heart rate dynamics derived from nonlinear dynamical systems theory, was decomposed into genetic and environmental components. Subjects were 196 male and 210 female middle-aged twins. Females showed larger HRV than men before (ApEn: p <.001; RSA: p =.052) and after adjustment for covariates (ApEn: p <.001; RSA: p =.015). This sex difference was confirmed by significant intrapair difference