A comparative meta-analysis of prospective observational studies on masked hypertension and masked uncontrolled hypertension defined by ambulatory and home blood pressure

Background: In a comparative meta-analysis, we investigated the prognostic value of masked hypertension and masked uncontrolled hypertension defined by ambulatory or home blood pressure (BP) monitoring. Methods: We searched English literature published till 2 September 2018 to identify prospective observational studies. Masked hypertension was defined as a normal clinic BP (<140/90 mmHg) in the presence of an elevated 24 h, daytime or night-time ambulatory or home BP. Clinical outcomes included all-cause and cardiovascular mortality, and fatal and nonfatal cardiovascular, stroke, cardiac, coronary and renal disease events. Results: In total, 21 studies (n = 130 318) were included. Overall, compared with normotensive participants, masked hypertensive patients had a 5.7/2.9 mmHg higher clinic BP and 18.7/9.8 mmHg higher out-of-office BP. The pooled risk ratio for masked hypertension versus normotension was 1.67 (95% confidence interval, 1.32–2.13) and 2.19 (1.72–2.78) for all-cause (eight studies) and cardiovascular mortality (three studies), respectively, and 1.71 (1.53–1.91), 1.95 (1.36–2.80), 1.76 (1.33–2.33), 1.62 (0.27–9.60), 3.85 (2.03–7.31) for fatal and nonfatal cardiovascular (15 studies), stroke (two studies), cardiac (two studies), coronary (two studies) and renal disease events (two studies), respectively. Risk ratios for all-cause mortality (1.78 versus 1.40, P = 0.16) and fatal and nonfatal cardiovascular events (1.81 versus 1.61, P = 0.29) were similar between studies on ambulatory and home BP monitoring in the overall analyses. The analyses in subgroups according to treatment status (untreated, treated or mixed) and sampling approach (population or referred patients) were confirmatory. Conclusion: Masked hypertension and masked uncontrolled hypertension were associated with unfavorable clinical outcomes, regardless of the out-of-office BP monitoring techniques.