Setting thresholds to varying blood pressure monitoring intervals differentially affects risk estimates associated with white-coat and masked hypertension in the population

Abstract

Outcome-driven recommendations about time intervals during which ambulatory blood pressure should be measured to diagnose white-coat or masked hypertension are lacking. We cross-classified 8237 untreated participants (mean age, 50.7 years; 48.4% women) enrolled in 12 population studies, using ≥140/≥90, ≥130/≥80, ≥135/≥85, and ≥120/≥70 mm Hg as hypertension thresholds for conventional, 24-hour, daytime, and nighttime blood pressure. White-coat hypertension was hypertension on conventional measurement with ambulatory normotension, the opposite condition being masked hypertension. Intervals used for classification of participants were daytime, nighttime, and 24 hours, first considered separately, and next combined as 24 hours plus daytime or plus nighttime, or plus both. Depending on time intervals chosen, white-coat and masked hypertension frequencies ranged from 6.3% to 12.5% and from 9.7% to 19.6%, respectively. During 91 046 person-years, 729 participants experienced a cardiovascular event. In multivariable analyses with normotension during all intervals of the day as reference, hazard ratios associated with white-coat hypertension progressively weakened considering daytime only (1.38; P=0.033), nighttime only (1.43; P=0.0074), 24 hours only (1.21; P=0.20), 24 hours plus daytime (1.24; P=0.18), 24 hours plus nighttime (1.15; P=0.39), and 24 hours plus daytime and nighttime (1.16; P=0.41). The hazard ratios comparing masked hypertension with normotension were all significant (P<0.0001), ranging from 1.76 to 2.03. In conclusion, identification of truly low-risk white-coat hypertension requires setting thresholds simultaneously to 24 hours, daytime, and nighttime blood pressure. Although any time interval suffices to diagnose masked hypertension, as proposed in current guidelines, full 24-hour recordings remain standard in clinical practice.

Keywords: ambulatory blood pressure monitoring; cardiovascular risk; masked hypertension; population science; white-coat hypertension.

Figure 1

Risk of a cardiovascular end point associated with white-coat and masked hypertension vs stringently defined normotension defined by various intervals of ambulatory monitoring. Definition of the blood pressure cross-classifications is given in the Methods and in the footnote to Table 2. In this analysis, we applied the most stringent definition of normotension as unique reference in which the conventional blood pressure was normal and that the ambulatory blood pressure was within normal limits for 24 hours plus daytime and nighttime. Hazard ratios express the risk compared with normotension and were adjusted for sex, age, body mass index, smoking, drinking, total cholesterol, diabetes mellitus, history of cardiovascular disease, and cohort. Horizontal bars denote the 95% confidence interval of the hazard ratios.

Figure 2

Risk of a cardiovascular end point associated with white-coat and masked hypertension vs stringently defined hypertension defined by various intervals of ambulatory monitoring. Definition of the blood pressure cross-classifications is given in the Methods and in the footnote to Table 2. In this analysis, we applied the most stringent definition of hypertension as unique reference in which the conventional blood pressure was over the threshold and that the ambulatory blood pressure was over the thresholds for 24 hours plus daytime and nighttime. Hazard ratios express the risk compared with hypertension and were adjusted for sex, age, body mass index, smoking, drinking, total cholesterol, diabetes mellitus, history of cardiovascular disease, and cohort. Horizontal bars denote the 95% confidence interval of the hazard ratios.