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Background Orthostatic blood pressure (BP) and heart rate (HR) responses are known to be impaired in older adults. The baroreflex, a mechanoreceptor based neural reflex, is known to govern short-term blood pressure regulation. Few studies have examined the relationship between baroreflex sensitivity (BRS), arterial stiffness and orthostatic BP and HR responses at an epidemiological level. Here we address this issue.
Methods Participants were recruited from a nationally representative cohort study. Beat-to-beat systolic BP (SBP) and diastolic BP (DBP) and heart rate (HR) responses to standing were analysed. Baroreflex sensitivity (ms/mmHg) was derived using 5 minutes of resting supine data and arterial stiffness was estimated using pulse wave velocity (PWV-m/s). Quartiles of BRS and PWV were calculated. Cross-sectional relationships between quartiles of BRS, PWV and orthostatic BP and HR recovery parameters were estimated by separate linear regression models after adjusting for age, gender, comorbidities, medications, baseline BP status. P < 0.004 was assumed significant to correct for multiple testing effects.
Results A sample of N = 4269 participants had complete data sets (age 61.0 SD (0.13) years; 54.5% female). Median BRS was 5.5 ms/mmHg (IQR:3.9-7.8) and median PWV was 10.2 m/s (IQR:9.0-11.7). Increasing BRS (quartile 4 compared to quartile 1) was associated with higher initial heart rate reactivity (β = 6.26 [5.49,7.03]; P < 0.001) but larger initial drops in SBP (β = -2.63 [-4.13,-1.13]; P < 0.001) and DBP (β = -2.10 [-3.00,-1.19]; P < 0.001). Increasing arterial stiffness was significantly associated with poorer SBP (β = -2.72 [-4.29,-1.15]; P < 0.001) and DBP (-2.19 [-2.98,-1.39]; P < 0.001) stabilisation after 40 seconds of standing.
Conclusion Measures of BRS are associated with the early stages of the hemodynamic response to standing, while PWV is related to impaired BP stabilisation over the first 40 seconds after standing. Future work will explore the longitudinal implications of these findings.