Effects of age and gender on autonomic control of blood pressure dynamics

Both age and gender influence cardiovascular autonomic control, which in tu rn may influence the ability to withstand adverse cardiac events and respon d to orthostatic stress. The purpose of this study was (1) to quantify age- and gender- related alterations in autonomic control of blood pressure (BP ) and (2) to examine the impact of these autonomic alterations on BP respon se to orthostatic stress. We measured continuous BP and R-R intervals and v asoactive peptide levels in the supine and 60 degrees head-up tilt position s during paced respiration (0.25 Hz) in 89 carefully screened healthy subje cts (41 men, 48 women, aged 20 to 83 years), Data were analyzed by gender ( age adjusted) and by age group (gender adjusted). During tilt, women had gr eater decreases in systolic BP than men (-10.2+/-2 versus -1.2+/-3 mm Hg; P =0.02) and smaller increases in low-frequency (sympathetically mediated) BP power (P=0.02). Upright plasma norepinephrine was lower in women (P=0.02). Women had greater supine high-frequency R-R interval power than men (P=0.0 001). In elderly subjects, the tilt-induced increase in low-frequency BP po wer was also diminished (P=0.01), despite higher supine (P=0.02) and simila r upright norepinephrine levels compared with younger subjects. Thus, healt hy women have less sympathetic influence on BP and greater parasympathetic influence on R-R interval than men, Elderly subjects also have reduced symp athetic influence on BP, but this appears to be more consistent with a redu ction in vasomotor sympathetic responsiveness.