6A.08

Abstract

Objective: While South Africa has one of the highest rates of hypertension globally, data on masked and white coat hypertension in the region is scant. This study sought to determine the frequency of masked and white coat hypertension in low income South African adults and to evaluate cardiovascular risk through measures of arterial stiffness. Design and method: We included 81 low income adults (50% men, 96% black, 4% coloured) aged 19–63 years, and measured clinic blood pressure four times (twice on each upper arm) with the Omron M10-IT automated device; also 24 hour ambulatory blood pressure with pulse wave analysis (Mobil-O-Graph ABPM), anthropometry and HIV status. We collected sociodemographic, stress and depression data by questionnaires. Results: When viewing hypertension criteria for both clinic and ambulatory BP, we found that 15% complied to all criteria, classified as sustained hypertensives; 3% had white coat hypertension; and 48% had masked hypertension. The sustained hypertension group had a higher mean body mass index and waist circumference than both the masked hypertension and normotensive groups (p = 0.004 and p = 0.007). Both the sustained hypertensives and masked hypertensives presented elevated 24-hour, daytime and nighttime pulse wave velocity compared to normotensives (all p < 0.001), but we found no differences between the sustained and masked hypertensives for pulse wave velocity and augmentation index. Other traditional cardiovascular risk factors including smoking, alcohol consumption, physical activity levels, occupation, stress or depression were also comparable between sustained and masked hypertensives. Conclusions: Almost half of African adults measured had masked hypertension and individuals presented comparable estimates for arterial stiffness to Africans with sustained hypertension. Since masked hypertension cannot be detected by clinic blood pressure measurement alone, these results may have far-reaching implications in hypertension detection, treatment and control strategies, and imply underestimations of country-specific hypertension prevalence rates. Further studies are required to determine the most cost effective method to detect undiagnosed hypertension cases in the African region.