Masked Hypertension and Cardiovascular Disease Events in a Prospective Cohort of Blacks: The Jackson Heart Study

Masked hypertension, defined as nonelevated clinic blood pressure (BP) with elevated out-of-clinic BP, has been associated with increased cardiovascular disease (CVD) risk in Europeans and Asians. Few data are available on masked hypertension and CVD and mortality risk among blacks. We analyzed data from the Jackson Heart Study, a prospective cohort study of blacks. Analyses included participants with clinic-measured systolic/diastolic BP <140/90 mm Hg who completed ambulatory BP monitoring after the baseline examination in 2000 to 2004 (n=738). Masked daytime (10:00 AM–8:00 PM) hypertension was defined as mean ambulatory systolic/diastolic BP ≥135/85 mm Hg. Masked nighttime (midnight to 6:00 AM) hypertension was defined as mean ambulatory systolic/diastolic BP ≥120/70 mm Hg. Masked 24-hour hypertension was defined as mean systolic/diastolic BP ≥130/80 mm Hg. CVD events (nonfatal/fatal stroke, nonfatal myocardial infarction, or fatal coronary heart disease) and deaths identified through December 2010 were adjudicated. Any masked hypertension (masked daytime, nighttime, or 24-hour hypertension) was present in 52.2% of participants; 28.2%, 48.2% and 31.7% had masked daytime, nighttime, and 24-hour hypertension, respectively. There were 51 CVD events and 44 deaths during a median follow-up of 8.2 and 8.5 years, respectively. CVD rates per 1000 person-years (95% confidence interval) in participants with and without any masked hypertension were 13.5 (9.9–18.4) and 3.9 (2.2–7.1), respectively. The multivariable adjusted hazard ratio (95% confidence interval) for CVD was 2.49 (1.26–4.93) for any masked hypertension and 2.86 (1.59–5.13), 2.35 (1.23–4.50), and 2.52 (1.39–4.58) for masked daytime, nighttime, and 24-hour hypertension, respectively. Masked hypertension was not associated with all-cause mortality. Masked hypertension is common and associated with increased risk for CVD events in blacks.