Assessment of cardiac autonomic control by heart period variability in patients with early-onset familial obesity.

For quantitative assessment of cardiac autonomic control, time and frequency domain measures of heart period variability were calculated by 24 h Holter recording in 10 young obese women with early-onset familial obesity and in 10 control subjects. Ultra low frequency and very low frequency power were lower in obese subjects than in controls (P < 0.05). High frequency power, a pure measure of vagal tone, was comparable between the two groups. However, low frequency power, which analysed over a 24 h Holter recording reflects parasympathetic more than sympathetic activity, was slightly lower in obese subjects than in controls (P = 0.06). Body mass index showed an inverse correlation with total power (r = -0.62; P < 0.05) and separately with ultra low (r = -0.59; P < 0.01), very low (r = -0.64; P < 0.005), low (r = -0.61; P < 0.005) and high frequency power (r = -0.53; P < 0.05). These results demonstrate a parasympathetic withdrawal increasing body weight. The reduction of ultra low frequency and very low frequency power, which are associated with sudden death, may help to explain the higher cardiovascular risk in obesity.