[Age dependency of heart rate variability, blood pressure variability and baroreflex sensitivity]

Objective. To compare the cardiovascular autonomic regulatory function between young and middle-aged male subjects and to assess the effects of aging. Method. Spectral indices of short term heart rate variability (HRV), systolic blood pressure variability (SBPV), and baroreflex sensitivity (BRS) in both supine and upright positions were obtained by AR spectral analysis and the sequential method, respectively, for both groups. Result. HRV spectral indices in both supine and upright, and the BRS in supine were lower in the middle-aged subjects than in the young subjects (P< 0.05, or P< 0.01). From supine to upright position total power (TP), low frequency power (LF) and high frequency power (HF) of HRV spectrum did not show any significant changes in the middle-aged subjects, whereas in the young subjects typical changes were observed. SBPV spectral indices did not show significant differences between the two groups in both supine and upright positions. However, SBPV HF was an exception, being lower in supine position in the middle-aged than in the young subjects (P< 0.01). For the young subjects, in supine position, BRS was correlated with LF and HF of HRV, respectively, and the spectral indices of HRV in supine position were also correlated with their corresponding indices in upright position. For the middle-aged subjects these correlations did not exist. Conclusion. In the middle-aged, both HRV and BRS are reduced and the correlations between HRV indices and BRS are not existent. However, the short-term blood pressure variability seems to be not age-dependent. It suggests that different regulatory mechanisms might account for it and that under resting condition the feed forward regulation from HRV to SBPV might be unimportant.