What Is the Significance of Masked Hypertension Versus Incident Hypertension in Blacks?

Abstract

T reatment-naive masked hypertension has been defined as discordant in-office normotension (<140/<90 mm Hg) versus out-of-office hypertension (≥135/85 mm Hg) for either home blood pressure (BP) monitoring (HBPM) or ambulatory BP monitoring (ABPM) of daytime ABPM (≥135/85 mm Hg), night-time ABPM (≥120/70 mm Hg), 24-hour ABPM (≥130/80 mm Hg), or a combination of these out-of-office BP subtypes. Masked hypertension may be a precursor of sustained hypertension, remain masked hypertension for a prolonged period of time, and occasionally revert to normotension.1 However, there are at least 5 other aspects of masked hypertension of clinical importance: (1) it has been considered an intermediate phenotype between sustained normotension and sustained hypertension, which most frequently arises from antecedent high-normal BP (130-139/85-89 mm Hg), less frequently from antecedent normal BP (120-129/80-84 mm Hg); and least frequently from antecedent optimal BP (<120/<80 mm Hg) 1 (note that normal and high-normal BP when combined are called prehypertension); (2) it frequently is associated with hypertensive target organ damage even without progressing to hypertension, perhaps because of increased pressure burden in daily life, and despite a long-dormant period before transitioning to sustained hypertension 1 ; (3) it has been associated with many cardiometabolic abnormalities, including obesity, metabolic syndrome, diabetes mellitus, obstructive sleep apnea, and chronic renal disease 1 ; (4) it frequently has been associated with nocturnal hypertension and impaired nocturnal dipping of BP-a particularly high-risk phenotype 2 ; and (5) there is an especially high prevalence of masked hypertension in people of African descent, approaching 30% to 50% in some series. [3][4][5][6] It is with this background that the present investigators used ABPM to define masked hypertension as a possible precursor of incident clinic hypertension in 317 treatment-naive participants from the Jackson Heart Study, a prospective cohort of blacks. 7 The mean age of this group was 54.8 years, mean body mass index was 30.1 U, prevalence of diabetes mellitus was 11.7%, any masked hypertension subtype was 45.4%, and the presence of left ventricular hypertrophy was 11.1%. Incident clinic hypertension was defined as the first visit with either clinic systolic/diastolic BP ≥140/90 mm Hg or initiation of antihypertensive medication. With a median follow-up of 8.1 years, representing study visits in 2005 to 2008 and 2009 to 2012, there were 187 (59%) incident cases of clinic hypertension: 79% and 42% of participants with and without any masked hypertension, respectively. Thus, the major new finding is that individuals with any subtype of masked hypertension-daytime, night-time, or 24-hour ABPM-had twice the risk for developing incident clinic hypertension when compared with those with antecedent sustained normotension. These proportions between masked hypertension and sustained normotension were generally consistent when assessing daytime, night-time, or 24-h...