Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Texas, USA.
The University of Texas Southwestern Medical Center, Dallas, Texas, USA.
J Physiol. 2020 Aug;598(16):3331-3341. doi: 10.1113/JP279877. Epub 2020 Jun 16.
In this study, we focused on muscle sympathetic nerve activity (MSNA) burst size and occurrence separately as subcomponents of the sympathetic baroreflex in older adults, and we found that the distribution (variation) of burst size against burst occurrence was greater in women than men. Older women had greater carotid artery stiffness compared with older men, while blood pressure (BP) distribution (variation) was comparable between sexes. Sympathetic baroreflex sensitivity assessed with burst incidence was less sensitive as the carotid artery became stiffer in older men and women, while that assessed with burst area was more sensitive as the carotid artery became stiffer in older women but not in older men. These results help us understand the mechanisms underlying the compensation for the impaired response of MSNA burst occurrence in older women with greater carotid artery stiffness to regulate BP similar to that in older men.
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 β-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 β-stiffness was greater in older women than men (6.7 ± 2.7 vs. 5.1 ± 2.7, P = 0.027). Sympathetic BRS assessed with burst incidence was lower in older women than men (-2.3 ± 1.4 vs. -3.3 ± 1.4 bursts·100 beats mmHg , P = 0.007), while this sex difference was observed when assessed with burst area after adjusting for carotid β-stiffness (-116.1 ± 135.0 vs. -185.9 ± 148.2 a.u. burst mmHg , P = 0.040), but not before. Sympathetic BRS assessed with burst area was negatively (more sensitive) correlated with carotid β-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.
在这项研究中，我们分别关注了肌肉交感神经活动（MSNA）爆发大小和发生作为老年人大动脉压力反射中交感神经的亚成分。我们发现，与男性相比，女性的爆发大小与爆发发生之间的分布（变化）更大。与男性相比，老年女性的颈动脉硬化程度更大，而血压（BP）分布（变化）在性别之间相似。随着老年男女颈动脉变得越来越硬，用爆发发生率评估的交感神经反射敏感性降低，而用爆发面积评估的敏感性则随着老年女性颈动脉变硬而增加，但在老年男性中则没有。这些结果有助于我们理解在颈动脉僵硬程度较大的老年女性中，MSNA 爆发发生的受损反应通过调节 BP 来代偿的机制，与老年男性相似。
在老年人群中，动脉僵硬和血压（BP）的神经控制存在性别差异。我们研究了在爆发发生方面，与男性相比，女性的 BP 反应是否更大，但在爆发大小方面并非如此。通过肌肉交感神经活动的爆发间隔和面积分别评估爆发发生和大小，并且通过 61 名健康老年受试者（30 名男性（69±6 岁）和 31 名女性（68±6 岁）；平均值±标准差）在仰卧休息时评估这些指数的分布范围。此外，我们同时分析了爆发发生和面积的交感神经反射敏感性（BRS）。使用 B 型超声图像和颈动脉 BP 测量颈动脉 β-僵硬度。与男性相比，老年女性的爆发间隔范围更小（P=0.002），而爆发面积的范围没有差异。与男性相比，老年女性的颈动脉 β-僵硬度更大（6.7±2.7 与 5.1±2.7，P=0.027）。用爆发发生率评估的交感神经 BRS 在老年女性中低于男性（-2.3±1.4 与-3.3±1.4 次·100 次搏动·mmHg，P=0.007），而在用颈动脉 β-僵硬度调整后，这种性别差异仅在用爆发面积评估时观察到（-116.1±135.0 与-185.9±148.2 单位·mmHg 爆发，P=0.040），而在用爆发发生率评估时则不然。用爆发面积评估的交感神经 BRS 与老年女性的颈动脉 β-僵硬度呈负相关（更敏感）（r=-0.53，P=0.002），但与男性无关。这些数据表明，尽管颈动脉僵硬较大的老年女性的爆发发生反应受损，但在每个爆发的爆发大小内的反应仍增强了对压力反射 BP 控制的反应。
