Impaired autonomic control of heart rate and blood pressure in obesity: role of age and of insulin-resistance.

The objectives of this study were to investigate cardiac and peripheral autonomic nervous system changes in normotensive overweight or obese subjects and the possible relation between these changes and insulin resistance independent of age. The authors used spectral analysis to measure simultaneously the short-term variability of heart rate (HR) and blood pressure (BP) using a Finapres device, in 67 normotensive overweight or obese patients (age 37 +/- 12 y, body mass index [BMI] = 37 +/- 9 kg/m2) and 45 never-obese subjects (controls; age 41 +/- 13 y, BMI 22 +/- 2 kg/m2). The spectral density was determined in three situations: subjects in the supine position, spontaneously breathing; subjects in the supine with controlled breathing; and subjects standing. The insulin sensitivity of overweight and obese subjects was determined from homeostatic model assessment (HOMA). The variability of normalized low-frequency (LF) spectral analysis of both HR and BP was lower in overweight or obese subjects than in controls, in the supine and standing positions (p <0.01). Normalized LF spectral analysis was negatively correlated to BMI independent of age, whatever the position. Homeostatic model assessment values were negatively correlated to the normalized LF spectral of HR, systolic BP and diastolic BP, in the standing position independent of BMI and age (p <0.05). Normalized high frequency (HF) of HR during controlled breathing decreased with age but not with BMI. In normotensive overweight or obese subjects, changes in sympathetic nervous system modulation are strongly correlated to insulin resistance. Decreased HR and BP variability could partly account for the higher cardiovascular risk and incidence of sudden death in obese persons.