Differential effects of female aging on sympathetic blood pressure regulation at rest and during stress in humans.

Older female (OF) adults exhibit blunted resting sympathetic blood pressure (BP) transduction compared with young female (YF) adults, affecting BP regulation. However, studies often lack control over health factors like body composition or habitual physical activity. Therefore, we compared resting sympathetic BP transduction and neurovascular responses during cold pressor test (CPT) and end-expiratory apnea between YF (n = 12) and OF (n = 9) matched for several health factors. We measured beat-to-beat hemodynamics and muscle sympathetic nerve activity (MSNA). OF exhibited higher resting supine BP and MSNA (p < 0.001) than YF. OF exhibited blunted increases in mean BP and diastolic BP following spontaneous MSNA bursts at rest. During the CPT, OF exhibited a smaller percent increase in total MSNA (interaction effect: p = 0.001) but not MSNA burst frequency responses. Mean BP increases were not different between groups, but OF exhibited a higher ∆mean BP/∆MSNA burst frequency ratio (p = 0.003). During apnea, OF experienced a smaller percent MSNA increase in total MSNA (p < 0.05), larger mean BP increases (interaction effect: p = 0.031), and higher ∆mean BP/∆total MSNA ratio (p = 0.003). These findings suggest attenuated signal-averaged sympathetic BP transduction at rest but increased time-averaged sympathetic transduction to mean BP during cold and apneic laboratory stressors in OF.