Broader adaptive range of sympathetic burst size in response to blood pressure change in older women with greater arterial stiffness

摘要

There are sex differences in arterial stiffness and neural control of blood pressure (BP) among older adults. We examined whether the sympathetic response to BP is greater in older women than men in burst size but not burst occurrence. Burst occurrence and size were assessed with burst interval and area of muscle sympathetic nerve activity, respectively, and the distributions of these indices were evaluated by range during supine rest in 61 healthy older subjects (30 men (69 +/- 6 years) and 31 women (68 +/- 6 years); means +/- SD). Also, we analysed sympathetic baroreflex sensitivity (BRS) with burst occurrence and area simultaneously. Carotid beta-stiffness was measured with B-mode ultrasonic image and carotid BP. The range of burst interval was smaller in older women than men (P = 0.002), while there was no difference in the range of burst area. Carotid beta-stiffness was greater in older women than men (6.7 +/- 2.7vs. 5.1 +/- 2.7,P = 0.027). Sympathetic BRS assessed with burst incidence was lower in older women than men (-2.3 +/- 1.4vs. -3.3 +/- 1.4 bursts center dot 100 beats(-1) mmHg(-1),P = 0.007), while this sex difference was observed when assessed with burst area after adjusting for carotid beta-stiffness (-116.1 +/- 135.0vs. -185.9 +/- 148.2 a.u. burst(-1) mmHg(-1),P = 0.040), but not before. Sympathetic BRS assessed with burst area was negatively (more sensitive) correlated with carotid beta-stiffness in older women (r = -0.53,P = 0.002) but not men. These data suggest that the response of burst size within each burst is augmented for the baroreflex BP control despite the impaired response of burst occurrence in older women with greater carotid stiffness.