Relationship between Home Blood Pressure and the Onset Season of Cardiovascular Events: The J-HOP Study (Japan Morning Surge-Home Blood Pressure).

BACKGROUND The incidence of cardiovascular disease (CVD) increases during winter. The risk that elevated home blood pressure (BP) pose for CVD events that occur in each of four seasons is unclear. We conducted a post-hoc analysis using the dataset from a nationwide cohort, the Japan Morning Surge-Home Blood Pressure (J-HOP) study, to assess the association between home BP and winter-onset CVD events. METHODS J-HOP participants who had cardiovascular risks conducted morning and evening home BP measurements for a 14-day period and were followed-up for the occurrence of CVD events. RESULTS We analyzed 4258 participants (mean age 64.9 years; 47% male; 92% hypertensives) who were followed-up for an average of 6.2±3.8 years (26,295 person-years). We divided the total of 269 CVD events (10.2/1000 person-years) by the season of onset as follows: 82 in the winter and 187 in the other seasons (spring, summer, and autumn). In the Cox models adjusted for covariates and the season when home BPs were measured at baseline, morning home systolic BP (SBP) was associated with both winter-onset and other season-onset CVD events: hazard ratio (HR) for winter 1.22, 95% confidence interval (CI) 1.06-1.42 per 10 mmHg; HR for other seasons 1.11, 95%CI 1.00-1.23. Evening home SBP was associated with the other season-onset CVD events (HR 1.20, 95%CI 1.08-1.33 per 10 mmHg), but not with the winter-onset CVD events. CONCLUSIONS Our findings indicate that compared to evening home BP, morning home BP might be a superior predictor of winter-onset CVD events.