A comparison of morning blood pressure surge in African Americans and whites.

African Americans have twice the risk of suffering a stroke compared to whites, but the reasons for this disparity have yet to be elucidated. Recent data suggest that the morning blood pressure (BP) surge is an independent predictor of strokes. Whether African Americans and whites differ with respect to morning BP surge is unknown. African-American (n=183) and white (n=139) participants, age 18-65, were studied with 24-hour ambulatory BP monitoring. Morning surge was defined as morning BP minus the trough BP during sleep. The morning surge was significantly lower in African Americans than in whites (23 mm Hg vs. 27 mm Hg; both SEM=1.0; p=0.009). This relationship was no longer evident after adjusting for gender, age, and body mass index (23 mm Hg vs. 26 mm Hg; SE=1.0 and 1.1; p=nonsignificant). Morning BP surge is unlikely to account for differences in stroke incidence between African Americans and whites.