Sympathetic neural reactivity to mental stress differs in black and non-Hispanic white adults

Black adults have a higher risk of hypertension compared to non-Hispanic white (NHW) adults, but physiological mechanisms underlying this predisposition remain unclear. This study compared 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). Baseline mean arterial pressure (80±2 vs. 82±1 mmHg), heart rate (61±4 vs. 61±2 beats/min), MSNA (13±1 vs. 15±2 bursts/min), and 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. MSNA reactivity to mental stress was significantly higher in NHW compared to black adults (time x race, p=0.006), with a particularly divergent responsiveness during the first minute of mental stress in NHW (4±1 burst/min) and black (-2±2 burst/min; p = 0.022). Blood pressure and heart rate reactivity to mental stress was similar between groups. In summary, black participants demonstrated a lower MSNA responsiveness to mental stress compared to NHW adults. These findings suggest that despite a higher prevalence of hypertension, blacks do not appear to have higher neural and cardiovascular responsiveness to mental stress when compared to NHW.

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