Prevalence and Determinants of Masked Hypertension in Nigeria: The REMAH Study

Estimating the burden of hypertension in Nigeria hitherto relied on clinic blood pressure (BP) measurement alone. This excludes individuals with masked hypertension (MH), i.e., normotensive clinic but hypertensive out-of-clinic BP. Methods: In a nationally representative sample of adult Nigerians, we obtained clinic BP using auscultatory method and out-of-clinic BP by self-measured home BP with semi-automated oscillometric device. Clinic BP was average of 5 consecutive measurements and home BP was average of 3 days duplicate morning and evening readings. MH was clinic BP <140 mm Hg systolic and 90 mm Hg diastolic and home BP ≥135 mm Hg systolic and/or 85 mm Hg diastolic. Results: Among 933 participants, the prevalence of sustained hypertension, MH, and white-coat hypertension was 28.3%, 7.9%, and 11.9%, respectively. Among subjects whose clinic BP were in the normotensive range (n = 558), the prevalence of MH was 13%; 12% among untreated and 27% among treated individuals. The mutually adjusted odds ratios of having MH among all participants with normotensive clinic BP were 1.33 (95% confidence interval, 1.10-1.60) for a 10-year higher age, 1.59 (1.09-2.40) for a 10 mm Hg increment in systolic clinic BP, and 1.16 (1.08-1.28) for a 10 mg/dl higher random blood glucose. The corresponding estimates in the untreated population were 1.24 (1.03-1.51), 1.56 (1.04-2.44), and 1.16 (1.08-1.29), respectively. Conclusions: MH is common in Nigeria and increasing age, clinic systolic BP, and random blood glucose are the risk factors.