Seasonal Variation in Day-by-Day Home Blood Pressure Variability and Effect on Cardiovascular Disease Incidence

Background: Although day-by-day home blood pressure (BP) variability (BPV) has been associated with cardiovascular disease (CVD) risk, it remains unclear whether this association differs from season to season. The present study aimed to assess seasonal variation in day-by-day home BP variability and its association with CVD risk. Methods: We analyzed the data from a nationwide, prospective observational study, the J-HOP study (Japan Morning Surge-Home Blood Pressure), in which 14 consecutive days of home BP monitoring were conducted. The values of SD (SDsystolic BP [SBP]), coefficient of variation(SBP), and average real variability(SBP) of home SBP were used as indices of day-by-day home BPV. Results: Among 4231 participants (mean age, 64.9 +/- 10.9 years, 46.7% male, 91.5% hypertensives), all 3 day-by-day home BPV indices were lower in summer than winter after adjusting for confounding factors. In winter, SDSBP, coefficient of variation(SBP), and average real variability(SBP) were significantly associated with increased risk of CVD events (coronary artery disease, stroke, heart failure, and aortic dissection; adjusted hazard ratio [95%CI] per 1-SD of SDSBP, 1.26 [1.02-1.54]; coefficient of variation(SBP), 1.24 [1.02-1.52]; average real variability(SBP), 1.44 [1.17-1.77]). These relationships were also observed in the analysis of quartiles of BPV parameters (adjusted hazard ratio [95%CI] compared to the first quartile, fourth quartile of SDSBP 2.26 [1.06-4.85]; coefficient of variation(SBP) 2.96 [1.43-6.15]; average real variability(SBP) 2.73 [1.25-5.93]). In other seasons, however, there were no significant associations between day-by-day home BPV and CVD event risk. Conclusions: Our findings indicate that day-by-day home BPV measured in winter is more strongly associated with future CVD incidence than that measured in other seasons.