Elderly blacks had smaller upright total muscle sympathetic nerve activity than whites (162% vs 243%; P=0.003), but greater upright diastolic BP (80 vs 71 mmHg; P=0.008).
Cross-Sectional (n=30)
Does sympathetic neural responsiveness and pressor response to orthostasis differ between elderly blacks and elderly whites?
Elderly blacks exhibit a blunted sympathetic neural response but an enhanced diastolic blood pressure response to orthostasis compared to elderly whites, suggesting differences in vascular transduction or nonadrenergic vasoconstrictor mechanisms.
Absolute Event Rate: 162% vs 243%
p-value: p=0.003
Neural control of blood pressure (BP) has been reported to differ between young blacks and whites. We hypothesized that elderly blacks have enhanced sympathetic neural responses during orthostasis compared with elderly whites. Muscle sympathetic nerve activity, arm-cuff BP, and heart rate were recorded continuously, and cardiac output, stroke volume, and total peripheral resistance were measured intermittently during supine and 5-minute 60° upright tilt in 10 blacks (65 SD, 4 years; 4 women) and 20 whites (68 6 years; 8 women). We found that muscle sympathetic nerve activity burst frequency was similar between blacks and whites in the supine position (44 10 versus 42 7 bursts per minute) and during upright tilt (59 11 versus 60 9 bursts per minute; P=0.846 for race, P<0.001 for posture, and P=0.622 for interaction). However, upright total muscle sympathetic nerve activity was smaller in blacks than in whites (162 39 versus 243 112%; P=0.003). Systolic BP, heart rate, cardiac output, and stroke volume were not different between groups. Diastolic BP was similar in the supine position, increased in all of the subjects during tilting; upright diastolic BP was greater in blacks than in whites (80 10 versus 71 7 mmHg; P=0.008). Total peripheral resistance did not differ between blacks and whites in the supine position or during upright tilt (P=0.354 for race, P<0.001 for posture, P=0.825 for interaction). Thus, elderly blacks have a blunted sympathetic neural responsiveness but enhanced pressor response to orthostasis compared with elderly whites, which may be attributable to an augmented sympathetic vascular transduction and/or nonadrenergic vasoconstrictor mechanisms (ie, angiotensin II or the venoarteriolar response).
Okada et al. (Tue,) reported a cross-sectional. Black race vs. White race was evaluated on Upright total muscle sympathetic nerve activity (p=0.003). Elderly blacks had smaller upright total muscle sympathetic nerve activity than whites (162% vs 243%; P=0.003), but greater upright diastolic BP (80 vs 71 mmHg; P=0.008).