SEASONAL VARIATION IN PREVALENCE OF MASKED UNCONTROLLED HYPERTENSION IN GENERAL PRACTICE OUTPATIENTS

Abstract

Objective: Masked hypertension is generally known as a cardiovascular disease (CVD) risk factor at a same level comparable to sustained hypertension. However, there is no data on seasonal differences in the prevalence of masked hypertension in outpatients under hypertensive treatment in clinical practice. We thus assessed seasonal variation in prevalence of masked uncontrolled hypertension using dataset of the Japan Morning Surge-Home Blood Pressure (J-HOP) study. Design and method: The J-HOP study is a nation-wide prospective observational study to predict CVD events in clinical practice outpatients, and participants underwent home blood pressure (BP) measurements in the morning and evening for a 14-day period. Clinic and home BP levels, prevalence of masked uncontrolled hypertension were compared in participants divided by seasons when they measured HBP. Masked uncontrolled hypertension was defined as clinic BP < 140/90 mmHg and morning or evening home BP > 135/85 mmHg based on the current Japanese guideline. Results: Among 4271 participants (mean age, 64.9 ± 10.9 years; 47.0% male; 91.4% hypertensive patients, 67 institutions in various areas in Japan), morning home systolic BP was significantly lower in summer compared to other seasons (spring, 139.4 ± 15.5 mmHg; summer, 134.1 ± 15.6 mmHg; autumn, 139.4 ± 16.1 mmHg; winter, 140.3 ± 15.5 mmHg, p value < 0.01 in all comparison between summer and other seasons). Moreover, prevalence of masked uncontrolled hypertension was significantly higher in winter that that in summer (spring, 22.5%; summer, 18.1%; autumn, 22.7%; winter, 24.4%, p < 0.01 in comparison between summer and winter) (Figure). In multivariate logistic regression analysis, masked uncontrolled hypertension was lower in summer compared to spring as reference after adjusted host factors and clinic BP levels (odds ratio, 0.60; 95% confidence interval, 0.47 to 0.77, p < 0.001).Conclusions: The present study revealed prevalence of masked uncontrolled hypertension tended to be lower in summer. Measurement of home BP is thus more valuable than clinic BP for management of hypertension corresponding to changes of season.