Sex differences in spontaneous baroreflex measures across adulthood: a cross-sectional hemodynamic study

Background Sex and aging are both associated with autonomic cardiovascular regulation, but whether sex differences in spontaneous baroreflex function reflect differences in overall levels or distinct age-related trajectories remains unclear. This study evaluated sex differences in spontaneous baroreflex measures across adulthood and examined whether these associations varied with age. Methods We conducted a cross-sectional analysis of 984 healthy participants aged 18–92 years, including 595 women and 389 men. Spontaneous baroreflex sensitivity (BRS), sequence rate, and baroreflex effectiveness index (BEI) were derived from a prespecified 180-second resting segment. Multivariable models adjusted for age, body mass index, systolic and diastolic blood pressure, heart rate, and recording device. Sex-by-age interactions were formally tested in the full estimable sample and in participants aged ≤74 years, and generalized additive models were used to characterize age-related in participants aged ≤64 years. Age-restricted and bootstrap analyses were performed to evaluate robustness. Results Women had higher adjusted BRS than men (geometric mean ratio 1.177, 95% CI 1.071–1.293; P<0.001; FDR-adjusted P = 0.002) and a lower sequence rate (incidence rate ratio 0.849, 95% CI 0.752–0.959; P = 0.008; FDR-adjusted P = 0.013). The overall sex difference in BEI was not statistically significant (odds ratio 0.887, 95% CI 0.781–1.007; P = 0.065). BRS decreased with increasing age in both sexes in the primary GAM/trajectory analysis restricted to participants aged ≤64 years. Sex-by-age interaction tests were not significant for BRS, sequence rate, or BEI in the full estimable sample or in the ≤74- and ≤64-year restricted analyses, and the direction of the main sex effects remained consistent in age-restricted and bootstrap sensitivity analyses. Conclusions Women exhibited higher spontaneous BRS and lower sequence rates than men after multivariable adjustment, while BRS declined with age in both sexes. The absence of significant sex-by-age interactions suggests that sex differences are more evident in the overall level of spontaneous baroreflex function than in the pattern of age-related change. These findings provide a more refined characterization of sex-related autonomic differences across adulthood and support further validation in longitudinal cohorts.