Autonomic cardiovascular regulation in obesity

Obese persons suffer from an increased mortality risk supposedly due to car diovascular disorders related to either continuously lowered parasympatheti c or altered sympathetic activation. Our cross-sectional correlation study establishes the relationship between obesity and autonomic regulation as we ll as salivary cortisol levels. Three patient cohorts were sampled, coverin g ranges of body mass index (BMI) of 27-32 (n=17), 33-39 (n=13) and above 4 0 kg/m(2)(n=12), and stratified for age, sex and menopausal status. Autonom ic cardiovascular regulation was assessed by use of heart rate variability and continuous blood pressure recordings. Spectral analytical calculation ( discrete Fourier transformation) yields indices of sympathetic and parasymp athetic activation and baroreflex sensitivity. Morning salivary cortisol wa s concurrently collected. Contrary to expectation, BMI and waist/hip ratio (WHR) were inversely correlated with sympathetic activity. This was true fo r resting conditions (r=-0.48, P<0.001; r=-0.33, P<0.05 for BMI and WHR res pectively) and for mental challenge (r=-0.42, P<0.01 for BMI). Resting baro reflex sensitivity was strongly related to the degree of obesity at rest (B MI: r=-0.35, P<0.05) and for mental challenge (r=-0.53, P<0.001). Salivary cortisol correlated significantly with waist circumference (r=-0.34, P=0.05 ). With increasing weight, no overstimulation was found but a depression in sympathetic and parasympathetic activity together with a significant reduc tion in baroreflex functioning and in salivary cortisol levels.