Effect of age on adrenergic and vagal baroreflex sensitivity in normal subjects.

The baroreflex maintains a stable blood pressure (BP) by dynamically adjusting heart rate (vagal component) and total peripheral resistance (adrenergic component). Vagal baroreflex sensitivity (BRS-v) is widely used but no methodology existed to quantitate adrenergic baroreflex sensitivity (BRS-a) until we developed the indices of BP recovery time (PRT) and BRS-a. The aims of this study were to generate a normative database and to evaluate whether there is an age effect on the cardiovagal and adrenergic sensitivities. We evaluated recordings of heart rate (HR) and BP in 255 normal subjects during the Valsalva maneuver (VM) and determined both BRS-v and BRS-a sensitivities. PRT increased with age whereas all other parameters declined with age. The adrenergic parameters correlated well with each other but not significantly with BRS-v. The results indicate that both BRS-a and BRS-v become blunted with increasing age and that these indices behave independently of each other.