Masked hypertension and prehypertension: diagnostic overlap and interrelationships with left ventricular mass: the Masked Hypertension Study

Abstract

Background: Masked hypertension (MHT) and prehypertension (PHT) are both associated with an increase in cardiovascular disease (CVD) risk, relative to sustained normotension. This study examined the diagnostic overlap between MHT and PHT, and their interrelationships with left ventricular (LV) mass index (LVMI), a marker of cardiovascular end-organ damage.

Methods: A research nurse performed three manual clinic blood pressure (CBP) measurements on three occasions over a 3-week period (total of nine readings, which were averaged) in 813 participants without treated hypertension from the Masked Hypertension Study, an ongoing worksite-based, population study. Twenty-four-hour ambulatory blood pressure (ABP) was assessed by using a SpaceLabs 90207 monitor. LVMI was determined by echocardiography in 784 (96.4%) participants.

Results: Of the 813 participants, 769 (94.6%) had normal CBP levels (<140/90 mm Hg). One hundred and seventeen (15.2%) participants with normal CBP had MHT (normal CBP and mean awake ABP ≥135/85 mm Hg) and 287 (37.3%) had PHT (mean CBP 120-139/80-89 mm Hg). 83.8% of MHT participants had PHT and 34.1% of PHT participants had MHT. MHT was infrequent (3.9%) when CBP was optimal (<120/80 mm Hg). After adjusting for age, gender, body mass index (BMI), race/ethnicity, history of high cholesterol, history of diabetes, current smoking, family history of hypertension, and physical activity, compared with optimal CBP with MHT participants, LVMI was significantly greater in PHT without MHT participants and in PHT with MHT participants.

Conclusions: In this community sample, there was substantial diagnostic overlap between MHT and PHT. The diagnosis of MHT using an ABP monitor may not be warranted for individuals with optimal CBP.

Figure 1.. Diagnostic overlap between masked hypertension and prehypertension based on the mean of nine clinic blood pressure readings. Circle with solid line represent participants with masked hypertension. Circle with dotted line represent the participants with prehypertension. Of the 769 participants with normal clinic blood pressure, a total of 117 participants had masked hypertension and 287 participants had prehypertension. 98 participants had both masked hypertension (MHT) and prehypertension (PHT), constituting 83.8% (98/117) of those with MHT, and 34.1% (98/287) of those with PHT.

Figure 2.. Distribution of masked hypertension across clinic blood pressure categories in the normal range (<140/90 mm Hg) based on the mean of nine readings. Clinic blood pressure levels in the normal range were categorized as follows: mean SBP ≥130 mm Hg or mean DBP ≥85 mm Hg (with mean SBP <140 mm Hg and mean DBP <90 mm Hg); mean SBP ≥120 mm Hg or mean DBP ≥80 mm Hg (with mean SBP <130 mm Hg and mean DBP <85 mm Hg); mean SBP ≥110 mm Hg or mean DBP ≥75 mm Hg (with mean SBP <120 mm Hg and mean DBP <80 mm Hg); mean SBP ≥100 mm Hg or mean DBP ≥70 mm Hg (with mean SBP <110 mm Hg and mean DBP <75 mm Hg); and mean SBP <100 mm Hg and mean DBP <70 mm Hg. Of the 769 participants with normal clinic blood pressure, a total of 287 participants had prehypertension and 482 had optimal clinic blood pressure levels. The risk of masked hypertension was disproportionally concentrated among those participants with prehypertension. CBP, clinic blood pressure; DBP, diastolic blood pressure; MHT, masked hypertension; SBP, systolic blood pressure.