Effects of genetic vs. environmental factors on cardiovascular autonomic function: A twin study

Aims Cardiovascular autonomic function is often assessed in patients with diabetes by measuring heart rate variability and baroreflex sensitivity, the heritability of which is not fully understood. The present study was aimed to determine the effects of genetic and environmental factors on heart rate variability and baroreflex sensitivity in monozygotic and dizygotic adult healthy twin pairs. 

Methods A total of 101 (63 monozygotic, 38 dizygotic) adult twin pairs (n=202; mean age 44.3years) were investigated. Anthropometric variables and serum metabolic markers were measured, while environmental characteristics were evaluated by questionnaires. Linear and spectral indices of heart rate variability and baroreflex sensitivity were determined by non-invasive methods. All measurements were adjusted for age and gender (model1) and for all significantly relevant covariates (model2). Heritability A-C-E structural equation models were used for characterizing the proportion of additive genetic, shared and unshared environmental influences. 

Results Genetic influence of different cardiovascular autonomic indices was estimated between 10.3 and 39.4%, common environmental influence was found between 0.0 and 33.2%, while unshared environmental influence was observed between 60.6 and 81.4% in model1 analysis. In multivariable-adjusted heritability estimates (model2), the magnitude of the genetic effects decreased to 0.0%, common environmental influence was nearly unchanged (values between 4.4 and 14.5%), while unshared environmental influence slightly increased (values between 85.5 and 96.5%). 

Conclusions Unshared environmental but not genetic factors have substantial influence on cardiovascular autonomic function, suggesting that appropriate treatment of all modifiable environmental factors is of importance in order to prevent or ameliorate cardiovascular autonomic neuropathy.