Cardiac autonomic function in young, healthy adults: Influence of race and sex.

Non-Hispanic Black (BL) adults living in the United States are more likely to develop cardiovascular disease (CVD) compared with their non-Hispanic White (WH) counterparts. Although measures of cardiac autonomic function [i.e., spontaneous cardiac baroreflex sensitivity (BRS) and heart rate variability (HRV)] have a predictive value for CVD, studies investigating racial differences in cardiac autonomic function are limited and have reported conflicting results. Furthermore, sex differences are often not considered despite BL women having a high prevalence of CVD. We hypothesized that young BL men and women would exhibit lower cardiac BRS and HRV compared with their WH counterparts. Heart rate and beat-to-beat blood pressure were continuously recorded during 5 min of supine rest in 145 young (18-33 yr), healthy, BL (37 men, 38 women) and WH (39 men, 31 women) adults to assess cardiac BRS and HRV. Overall cardiac BRS (sequence method) was higher in BL adults compared with WH adults ( < 0.001), which was mainly driven by differences between BL and WH men (BL men: 34 ± 16 vs. WH men: 21 ± 9 ms/mmHg, < 0.001) compared with women (BL women: 27 ± 12 vs. WH women: 24 ± 11 ms/mmHg; > 0.05). Likewise, greater HRV in BL adults, indexed by root mean square of successive differences, was primarily driven by BL men (BL men: 109 ± 59 vs. WH men: 64 ± 33 ms; < 0.001) rather than BL women ( > 0.05). Thus, contrary to our hypothesis, these results support that reduced cardiac autonomic function does not manifest early in life among young BL adults. Herein, we demonstrated that BL adults do not have lower cardiac autonomic function compared with WH adults. Rather BL men had greater spontaneous cardiac baroreflex sensitivity and heart rate variability compared with WH men while no differences were found among BL and WH women. These findings suggest that reduced cardiac autonomic function, which could increase the risk of cardiovascular disease, does not appear early in life in healthy BL adults.