The hemodynamic responses to hot flushes and associated changes in sympathetic activity

Introduction: Menopausal hot flushes are associated with cardiovascular disease (CVD). The hemodynamic responses to hot flushes are heterogenous, with blood pressure (BP) dropping (responders) during some hot flushes yet not changing (non-responders) during others. Although hot flushes have been considered sympathoexcitatory, muscle sympathetic nerve activity (MSNA) has not been measured during hot flushes. We tested the hypothesis that MSNA will increase in the BP responder hot flushes but not during BP non-responder hot flushes. Methods: Twelve postmenopausal females (age: 57±7yrs, body mass index: 26±4kg/m2) experiencing ≥3 hot flushes/day completed a fasted study visit. Participants lay supine for two hours (one hour of spontaneous observation and one hour of heat-induced hot flush observation) while heart rate (HR; electrocardiography), BP (finger plethysmography) and MSNA (microneurography) were recorded. Twenty-two total hot flushes occurred. Hot flushes were considered responders if there was a decline of mean arterial BP (MAP) ≥8mmHg (determined via median split; n=11; MSNA n=8); the remaining hot flushes were considered non-responders (n=11; MSNA n=11). Data was averaged into 30-sec bins beginning 3min prior to each hot flush and ending 90sec after the participant reported the start of a hot flush. A repeated measures ANOVA was used to compare data between groups. Results: There were no differences in responder and non-responder BP or MSNA at start of the analysis period (p >0.05). There were time-by-group interactions for systolic BP (p< 0.01), diastolic BP (p< 0.01), MAP (p< 0.01), and MSNA burst frequency (BF; p=0.04) and a trend towards an interaction for MSNA burst incidence (BI; p=0.07), with responder BP decreasing (SBP:∆17±14mmHg; DBP:∆6±7mmHg; MAP:∆10±9mmHg) and MSNA increasing (MSNA BF:∆7±6bursts/min; MSNA BI:∆9±10bursts/100hb) with no changes in non-responder BP and MSNA (SBP: ∆4±9mmHg; DBP: ∆0.5±8mmHg; MAP: ∆2±8mmHg; MSNA BF: ∆3±8bursts/min; MSNA BI: ∆-2±11bursts/100hb). A significant time-by-group interaction was not observed, however, for HR (responder: ∆5±5bpm; non-responder: ∆7±6bpm; p=0.28). Conclusion: Blood pressure responder, but not BP non-responder, hot flushes were associated with a decrease in BP and an increase in MSNA. These findings suggest that females with BP responder hot flushes may experience sympathetic surges, contributing to autonomic dysregulation and a greater risk of CVD. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.