Sex and age effects on cardiovascular autonomic function in healthy adults.

PURPOSE: To determine the effects of sex and age on cardiovascular autonomic parameters in healthy adults as assessed by Finapres (finger arterial pressure) method and prolonged head-up tilt (HUT).
METHODS: We enrolled 81 healthy volunteers (41 females, 40 males, 18-74 years) for extensive cardiovascular autonomic function testing including blood pressure (BP) recordings, electrocardiography, and impedance cardiography at rest, under 60° HUT for 45 min, active standing for 5 min, Valsalva maneuver, and deep breathing (DB). Mean values and orthostatic changes, i.e., differences to baseline, of heart rate (HR), systolic and diastolic BP, stroke volume (SV), and total peripheral resistance (TPR), as well as DB ratio and Valsalva ratio were calculated. A generalized linear model (extended by generalized estimating equations) was used to assess sex- and age-related differences.
RESULTS: Mean HR at rest was higher in women than in men (p = 0.035). In men, we observed significantly higher mean BP at rest (p < 0.001 systolic and p = 0.004 diastolic) and during HUT (p = 0.001 systolic and p < 0.001 diastolic), mean TPR at rest (p = 0.034), and mean SV during HUT (p < 0.001). We found no significant impact of sex on orthostatic changes of HR and BP. Mean TPR during HUT increased with age (p = 0.001), particularly in older women. Orthostatic changes of HR and diastolic BP, DB ratio, and Valsalva ratio became attenuated with age (p = 0.018, p = 0.006, p < 0.001, and p < 0.001, respectively).
CONCLUSIONS: Our study suggests that aging rather than sex needs to be taken into account when interpreting HR and BP changes during prolonged HUT performance.