Masked and Incident Clinic Hypertension Among Blacks

Study Questions:

Masked hypertension (HTN), defined as nonelevated clinic blood pressure (BP) and elevated out-of-clinic BP, may be an intermediary stage in the progression from normotension to HTN. What is the association of out-of-clinic BP and masked HTN using ambulatory BP monitoring (ABPM) with incident clinic HTN in blacks?


The Jackson Heart Study, a prospective cohort of blacks, included 317 participants with clinic BP <140/90 mm Hg and complete ABPM, who were not taking antihypertensive medication at baseline in 2000-2004. Using the ABPM to characterize systolic BP and diastolic BP, masked daytime HTN was defined as mean daytime BP ≥135/85 mm Hg, masked night-time HTN as mean night-time BP ≥120/70 mm Hg, and masked 24-hour HTN as mean 24-hour BP ≥130/80 mm Hg. Incident clinic HTN, assessed at study visits in 2005-2008 and 2009-2012, was defined as the first visit with clinic systolic/diastolic BP ≥140/90 mm Hg or antihypertensive medication use.


Mean age was about 55 years, BMI was 30.1 kg/m2, 69% were female, about 12% were diabetic, and 57% had prehypertension (≥120/70 mm Hg). Any masked HTN was found in 45% and left ventricular hypertrophy (LVH) by echo-Doppler LV mass in 11.1%. Using any definition of masked HTN, 51.9% of participants with prehypertension and 14.7% of those with normal clinic BP developed masked HTN over the median 8.1-year follow-up. Clinic HTN developed in 79.2% and 42.2% of participants with and without any masked HTN, 85.7% and 50.4% with and without masked daytime HTN, 79.9% and 43.7% with and without masked night-time HTN, and 85.7% and 48.2% with and without masked 24-hour HTN, respectively. Multivariable-adjusted hazard ratios were two-fold for incident clinic HTN for any masked HTN subtype.


ABPM can identify blacks at increased risk for developing clinic hypertension.


There is a high prevalence of masked hypertension in blacks (range 30%-50%). It can be associated with hypertensive target organ damage even without progressing to clinic HTN, perhaps because of increased pressure burden in daily life. It has also been associated with cardiometabolic disorders and nocturnal hypertension and impaired nocturnal dipping of BP—a particularly high-risk phenotype. The inference from the study is that ABPM should be considered in normotensive blacks, particularly in those with prehypertension and LVH without HTN. However, as the authors admit, home BP monitoring was not part of their protocol, and if used in middle-aged and elderly blacks, could reveal the diagnosis of masked hypertension and earlier administration of treatment and possible prevention of target organ damage.

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