Abstract
PURPOSE: Neurogenic orthostatic hypotension (nOH) is the hallmark of neurodegenerative forms of autonomic failure, including pure autonomic failure, multiple system atrophy, and Parkinson's disease. Studies have shown autonomic physiological differences in Africans Americans (AA) such as lower heart rate variability, enhanced blood pressure reactivity, and blunted sympathetic neural response compared to non-Hispanic whites. However, the clinical characteristics and neurohormonal profile of autonomic failure in AA is unknown. METHODS: A total of 65 patients with nOH participated in this study (9 AA and 56 non-Hispanic whites). Both groups were of similar age and comorbidity status, and they underwent standardized autonomic testing and assessment of neurohormonal levels and renin activity and aldosterone in supine and upright positions. RESULTS: There were no significant differences in baseline autonomic clinical characteristics between non-Hispanic whites and AA with nOH. Non-Hispanic whites demonstrated a significant increase in upright renin activity compared to AA (295 ± 88% vs. 13 ± 13%, respectively). AA showed a blunted increase in aldosterone compared to non-Hispanic whites (188 ± 27% vs. 59 ± 38%, respectively). These results indicated persistent suppression of the renin-angiotensin system in AA, particularly during upright posture. CONCLUSION: Our findings demonstrate that AA with nOH have similar clinical characteristics and hemodynamic autonomic profiles, but lower upright renin activity and aldosterone levels, compared to non-Hispanic whites. Renin suppression persists in AA with severe autonomic failure and can potentially contribute to postural changes and supine hypertension.