ABSTRACT: BACKGROUND:Ambulatory blood pressure (BP) monitoring is the reference standard for out-of-clinic BP measurement. Thresholds for identifying ambulatory hypertension (daytime systolic BP [SBP]/diastolic BP [DBP] ?135/85 mm?Hg, 24-hour SBP/DBP ?130/80 mm?Hg, and nighttime SBP/DBP ?120/70 mm?Hg) have been derived from European, Asian, and South American populations. We determined BP thresholds for ambulatory hypertension in a US population-based sample of African American adults. METHODS:We analyzed data from the Jackson Heart Study, a population-based cohort study comprised exclusively of African American adults (n=5306). Analyses were restricted to 1016 participants who completed ambulatory BP monitoring at baseline in 2000 to 2004. Mean SBP and DBP levels were calculated for daytime (10:00 am-8:00 pm), 24-hour (all available readings), and nighttime (midnight-6:00 am) periods, separately. Daytime, 24-hour, and nighttime BP thresholds for ambulatory hypertension were identified using regression- and outcome-derived approaches. The composite of a cardiovascular disease or an all-cause mortality event was used in the outcome-derived approach. For this latter approach, BP thresholds were identified only for SBP because clinic DBP was not associated with the outcome. Analyses were stratified by antihypertensive medication use. RESULTS:Among participants not taking antihypertensive medication, the regression-derived thresholds for daytime, 24-hour, and nighttime SBP/DBP corresponding to clinic SBP/DBP of 140/90 mm?Hg were 134/85 mm?Hg, 130/81 mm?Hg, and 123/73 mm?Hg, respectively. The outcome-derived thresholds for daytime, 24-hour, and nighttime SBP corresponding to a clinic SBP ?140 mm?Hg were 138 mm?Hg, 134 mm?Hg, and 129 mm?Hg, respectively. Among participants taking antihypertensive medication, the regression-derived thresholds for daytime, 24-hour, and nighttime SBP/DBP corresponding to clinic SBP/DBP of 140/90 mm?Hg were 135/85 mm?Hg, 133/82 mm?Hg, and 128/76 mm?Hg, respectively. The corresponding outcome-derived thresholds for daytime, 24-hour, and nighttime SBP were 140 mm?Hg, 137 mm?Hg, and 133 mm?Hg, respectively, among those taking antihypertensive medication. CONCLUSIONS:On the basis of the outcome-derived approach for SBP and regression-derived approach for DBP, the following definitions for daytime, 24-hour, and nighttime hypertension corresponding to clinic SBP/DBP ?140/90 mm?Hg are proposed for African American adults: daytime SBP/DBP ?140/85 mm?Hg, 24-hour SBP/DBP ?135/80 mm?Hg, and nighttime SBP/DBP ?130/75 mm?Hg, respectively.
