Sex difference in cardiac autonomic function in African American adults

Abstract

African American (AA) individuals in the United States have the highest prevalence of hypertension, with an age-adjusted prevalence of 55.8% in AA men and 56.9% in women. Compared to other racial groups, the AA population also has a two- to three-fold higher mortality rate resulting from hypertension-related causes. Furthermore, AA men exhibit a higher mortality rate than AA women. Previous studies have demonstrated sex differences in some biological mechanisms linked to the increased cardiovascular disease risk in the AA population —such as impaired vascular function and elevated oxidative stress. However, it is unknown whether sex differences are present in baroreflex sensitivity (BRS) and heart rate variability (HRV), which are key mechanisms that may contribute to the pathogenesis and clinical outcomes of hypertension. Herein, we tested the hypothesis that young AA men exhibit impaired cardiac autonomic function (spontaneous BRS and HRV) compared to AA women. We studied 26 young normotensive AA adults (13 women) [Age (men: 22 ± 3; and women: 19 ± 1yr; mean ± SD, p = 0.03); BMI (men: 24 ± 3; and women: 24 ± 2 kg/m2; p = 0.92)]. Heart rate (HR; ECG) and beat-to-beat blood pressure (BP; finger plethysmography) were continuously recorded during 10 min of rest to assess HRV and cardiac BRS. Resting HR (men, 61 ± 8; and women: 65 ± 9 bpm; p = 0.18), diastolic BP (men, 66 ± 6; and women: 65 ± 5 mmHg; p = 0.48) and respiratory rate (men, 17 ± 3; and women, 17 ± 3 bpm; p = 0.97) were similar between the groups. Mean BP and systolic BP were higher in AA men, though within the normotensive range for both groups [mean BP (men: 84 ± 5; and women: 76 ± 5 mmHg; p = 0.001); SBP (men: 119 ± 4; and women: 103 ± 7 mmHg; p < 0.001)]. HRV [root mean square of successive differences between normal heartbeats (RMSSD); men, 113 ± 78; and women, 79 ± 43 ms; p = 0.18] and cardiac BRS (overall gain; men, 25 ± 13; and women, 28 ± 12 ms/mmHg; p = 0.66) were not different between groups. These results indicate that BRS and HRV, which are markers of cardiac autonomic regulation, do not differ based on sex among young normotensive African American individuals. Supported by: Kinesiology and Health Education UT Austin Start-up Account 19-2635-91; and TACSM 2023 Student Research Development Award. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.