Black Adults Display Reduced Sympathetic Reactivity to Mental Stress Compared to Non‐Hispanic White Adults

Abstract

Black adults have a higher risk of developing essential hypertension compared to non‐Hispanic white (NHW) adults, but the physiological mechanisms underlying this predisposition are not clearly elucidated. The purpose of this study was to compare muscle sympathetic nerve activity (MSNA) responses to mental stress in a group of young black and NHW participants. We hypothesized that the sympathoexcitation associated with mental stress would be greater in black adults compared to NHW. Thirty‐five male adults (19 black, 23±1 years; 16 NHW, 22±1 years) were examined during a 5 min supine baseline and 5 min of mental stress (via mental arithmetic). Neural and cardiovascular measurements included blood pressure (sphygmomanometer and beat‐to‐beat finger plethysomography), heart rate (HR; electrocardiogram), and MSNA (microneurography). Baseline mean arterial pressure (MAP; 72±2 vs. 77±2 mmHg), HR (68±4 vs. 66±4 beats/min), MSNA (13±1 vs. 15±3 bursts/min), and spontaneous sympathetic baroreflex sensitivity (−1.1 ± 0.4 vs −1.5 ± 0.3 bursts/100hb/mmHg) were not significantly different between NHW and black adults (p>0.05), respectively. Systolic arterial pressure (SAP) responsiveness to mental stress was significantly higher in NHW compared to black adults (time × race, p=0.028). Likewise, MSNA reactivity to mental stress was significantly higher in NHW compared to black adults (time × race, p=0.017), with a particularly divergent responsiveness during the first minute of mental stress in NHW (Δ4±1 burst/min) and black (Δ‐4±2 burst/min; p = 0.007). HR reactivity to mental stress was similar between the two groups (time × race, p=0.721). In summary, and contrary to our initial hypothesis, NHW participants demonstrated a higher MSNA responsiveness to mental stress compared to black adults. These findings suggest that although black adults have a higher prevalence of essential hypertension, they do not appear to have higher neural and cardiovascular responsiveness to mental stress when compared to NHW.