SEASONAL VARIATION OF MASKED UNCONTROLLED NOCTURNAL HYPERTENSION MEASURED BY NIGHTIME HOME BLOOD PRESSURE: THE J-HOP NOCTURNAL BLOOD PRESSURE STUDY

Abstract

Objective: Usual daytime (morning and evening) home blood pressure (BP) monitoring can not detect nighttime hypertension. Masked uncontrolled nocturnal hypertension is defined as uncontrolled nighttime BP nonetheless controlled usual daytime home BP (HBP). Although previous studies have reported seasonal variation of nighttime BP evaluated by ambulatory BP monitoring is higher in summer than winter, seasonal variation in prevalence of masked uncontrolled nocturnal hypertension evaluated by nighttime HBP measurements remains unclear. Hence, we assessed the seasonal variation in nighttime HBP and the prevalence of masked uncontrolled nocturnal hypertension using a dataset of the Japan Morning Home-Surge BP (J-HOP) Nocturnal BP study. Design and method: This is a cross-sectional, post-hoc analysis using the dataset of the J-HOP Nocturnal BP study, which recruited patients with a history of or risk factors of cardiovascular disease. Participants underwent consecutive 14-day HBP measurements (morning and evening) and nighttime HBP measurements (a.m. 2, 3, and 4). We divided participants into four groups in each season. Masked uncontrolled nocturnal hypertension was defined as controlled daytime HBP (mean of morning and evening home systolic BP [SBP] < 135 mmHg and diastolic BP [DBP] < 85 mmHg) and uncontrolled nocturnal HBP (mean nighttime home SBP >= 120 or DBP >= 70 mmHg). Results: Among 2545 participants (age, 63.3 ± 10.3 yrs; 49% of male; antihypertensive medication use, 82.6%), 629, 596, 719, and 601 participants were enrolled in spring, summer, autumn, and winter, respectively. Nighttime home SBP/DBP were higher in summer than winter (SBP/DBP in summer, 123.3 ± 14.6/70.4 ± 8.9 mmHg; vs. in winter, 119.3 ± 14.0/69.1 ± 8.4 mmHg, p < 0.05). In 1490 participants with controlled daytime HBP, moreover, the prevalence of masked uncontrolled nocturnal hypertension was higher in summer than other seasons (summer, 55.7% vs. spring, 41.8%; vs. autumn, 42.9%; vs. winter, 39.7%, all p < 0.01). These relationships were also observed in multivariate logistic regression analysis (Table). Conclusions: In the present study, we revealed the prevalence of masked uncontrolled nocturnal hypertension was higher in summer than other seasons.