Abstract 2993: Impact of Masked Hypertension in an Urban Developing Community in South Africa
Introduction. Masked hypertension, where ambulatory blood pressure (ABP) is raised despite normal conventional BP (CBP), may not be benign.
Hypothesis. We hypothesised that masked hypertension has the same prevalence and impact on left ventricular mass and dimensions in subjects of African descent as reported in other population groups.
Methods. We studied 472 randomly selected subjects of African descent living in urban developing communities around Johannesburg (minimum age of 17 years), of whom 336 had successful ABP (Spacelab model 90207) monitoring and clinic CBP measurements. Left ventricular mass and geometry were determined using echocardiography in 185 consenting subjects. CBP measurement procedures were standardized and conducted by trained observers (non-physicians).
Results. ~8% of subjects had a normal CBP, but a raised 24-hour and/or daytime BP based on thresholds cited in published guidelines. ~6% of subjects had a normal CBP, but a raised 24-hour and/or daytime BP based on upper 95% confidence intervals for ABP determined in 190 subjects with normal office BP values. Mean 24-hour, daytime and night-time BP values in masked hypertensives were higher than normotensives (p < 0.001), but lower than uncontrolled hypertensives (p < 0.05). As compared to normotensive subjects, uncontrolled hypertensives were older and had a higher body mass index (BMI) and subjects with masked hypertension were of an intermediate age (p < 0.01 versus both normotensives and uncontrolled hypertensives) but had a similar BMI. After adjusting for age, sex and BMI, uncontrolled hypertensives had a higher left ventricular (LV) posterior (p < 0.005) and septal (p < 0.005) wall thickness and LV mass index (56 ± 20 g/m2.7) in comparison to normotensives (LV mass index = 44 ± 8 g/m2.7, p < 0.005). In contrast, after adjusting for covariates, masked hypertensives had LV wall thickness and LV mass index (45 ± 14 g/m2.7) values comparable with normotensives.
Conclusions. As compared to communities of European and Asian descent, a similar prevalence (~8%) of masked hypertension occurs in adult subjects in an urban, developing, community in South Africa. However, masked hypertension in subjects of African descent is not associated with an increased LV mass.