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 aut onomic nervous system changes in normotensive overweight or obese subjects and the possible relation between these changes and insulin resistance inde pendent of age. The authors used spectral analysis to measure simultaneousl y the short-term variability of heart rate (HR) and blood pressure (BP) usi ng a Finapres device, in 67 normotensive overweight or obese patients (age 37 +/- 12 y, body mass index [BMI] = 37 +/- 9 kg/m(2)) and 45 never-obese s ubjects (controls; age 41 +/- 13 y, BMI 22 +/- 2 kg/m(2)). The spectral den sity was determined in three situations: subjects in the supine position, s pontaneously breathing; subjects in the supine with controlled breathing, a nd subjects standing. The insulin sensitivity of overweight and obese subje cts was determined from homeostatic model assessment (HOMA). The variabilit y 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 s tanding positions (p <0.01). Normalized LF spectral analysis was negatively correlated to BMI independent of age, whatever the position. Homeostatic m odel assessment values were negatively correlated to the normalized LF spec tral of HR, systolic BP and diastolic BP, in the standing position independ ent of BMI and age (p <0.05). Normalized high frequency (HF) of HR during c ontrolled breathing decreased with age but not with BMI. In normotensive ov erweight or obese subjects, changes in sympathetic nervous system modulatio n are strongly correlated to insulin resistance. Decreased HR and BP variab ility could partly account for the higher cardiovascular risk and incidence of sudden death in obese persons.