Key result
African American ethnicity was associated with blunted SBP dipping compared to whites (P=0.01), but this difference was diminished when accounting for BMI, sleep quality, and sympathetic activity.
Cross-Sectional (n=128)
p-value: p=0.01
Ethnic differences in blood pressure dipping between African Americans and whites appear to be largely driven by differences in BMI, sleep quality, and sympathetic nervous system activity.
Sleep and SNS factors may mediate ethnic BP dipping differences; leaves open whether targeting them improves outcomes.
BACKGROUND: Blunted blood pressure (BP) dipping is an established predictor of adverse cardiovascular outcomes. Although blunted BP dipping is more common in African Americans than whites, the factors contributing to this ethnic difference are not well understood. This study examined the relationships of BP dipping to ethnicity, body mass index (BMI), sleep quality, and fall in sympathetic nervous system (SNS) activity during the sleep-period. METHODS: On three occasions, 128 participants with untreated high clinic BP (130-159/85-99 mm Hg) underwent assessments of 24-h ambulatory BP (ABP), sleep quality, (evaluated by sleep interview, self-report, actigraphy) and sleep-period fall in sympathetic activity (measured by waking/sleep urinary catecholamine excretion). RESULTS: Compared to whites (n = 72), African Americans (n = 56) exhibited higher sleep-period systolic (SBP) (P = 0.01) and diastolic BP (DBP) (P < 0.001), blunted SBP dipping (P = 0.01), greater BMI (P = 0.049), and poorer sleep quality (P = 0.02). SBP dipping was correlated with BMI (r = -0.32, P < 0.001), sleep quality (r = 0.30, P < 0.001), and sleep-period fall in sympathetic activity (r = 0.30, P < 0.001). Multiple regression analyses indicated that these three factors were independent determinants of sleep-period SBP dipping; ethnic differences in dipping were attenuated when controlling for these factors. CONCLUSIONS: Blunted BP dipping was related to higher BMI, poorer sleep quality, and a lesser decline in sleep-period SNS activity. Although African-American ethnicity also was associated with blunted dipping compared to whites in unadjusted analyses, this ethnic difference was diminished when BMI, sleep quality, and sympathetic activity were taken into account.
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Sherwood et al. (2011) conducted a cross-sectional in untreated high clinic BP (n=128). African American ethnicity vs. White ethnicity was evaluated on sleep-period SBP dipping (p=0.01). African American ethnicity was associated with blunted SBP dipping compared to whites (P=0.01), but this difference was diminished when accounting for BMI, sleep quality, and sympathetic activity.
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