Sleep-Time Blood Pressure and the Prognostic Value of Isolated-Office and Masked Hypertension

BACKGROUND Elevated sleep-time blood pressure (BP) is a better predictor of cardiovascular risk than the awake or 24 h BP means. However, discrepancies in the diagnosis of hypertension between clinic and ambulatory measurements (isolated-office and masked hypertension) are frequently defined by comparing clinic with only awake BP. We evaluated the impact of sleep-time BP in the prognostic value of isolated-office and masked hypertension. METHODS We studied 3,344 subjects (1,718 men/1,626 women), 52.6 +/- 14.5 years of age, during a median 5.6-years follow-up. Ambulatory BP was measured for 48 h at baseline, and again annually or more frequently (quarterly) after treatment adjustments in hypertensive subjects. RESULTS Out-of-office (masked and sustained) hypertension was associated with higher cardiovascular risk than normotension and isolated-office hypertension (P < 0.001) only when those conditions were defined on the basis of asleep, but not on awake or 24 h BP mean. Using only awake pressure for classification, 58.2% of subjects with masked hypertension were mistakenly classified as normotensive, and 26.3% of subjects with sustained hypertension were erroneously identified as isolated-office hypertensive. Cox proportional-hazard analysis using the awake and asleep pressure means as potential predictors of cardiovascular risk and adjusted for significant confounders revealed that only asleep mean was an independent significant predictor of outcome. CONCLUSIONS Subjects with elevated sleep-time BP are at high cardiovascular risk, independently of either clinic or ambulatory awake measurements. Sleep-time BP determined by ambulatory monitoring should thus be used for proper identification of out-of-office hypertension, a condition associated with markedly increased cardiovascular risk.