Factors Associated With Day-By-Day Variability of Self-Measured Blood Pressure at Home: The Ohasama Study

BACKGROUND: We previously reported that high day-by-day blood pressure (BP) variability derived from self-measured BP at home (home BP) predicted cardiovascular mortality over and beyond other risk factors. The objective of this study is to clarify the determinants of the day-by-day home-BP variability. METHODS: We conducted a cross-sectional community survey in 1,215 inhabitants (female gender 59%, mean age 62 years) of Ohasama, Japan. The subjects measured their BP and heart rate once every morning and once every evening for 4 weeks. The day-by-day BP variability and heart rate variability were defined as within individual standard deviation of all home BP and heart rate, respectively. We also considered coefficient of variation (CV). These parameters in the morning and those in the evening were calculated separately. RESULTS: The level and standard deviation of home systolic/diastolic BP (SBP/DBP) in the morning were 123.4 +/- 15.1/75.7 +/- 9.0 mm Hg and 8.6 +/- 3.1/5.8 +/- 2.0 mm Hg. Multivariate linear regression analysis demonstrated that older age, female gender, elevated home BP, low home heart rate, and elevated home heart rate variability were significant determinants of elevated home-BP variability. In addition to these factors, alcohol intake and sedentary lifestyle were also determinants of elevated home-BP variability in the evening. CONCLUSIONS: Day-by-day home-BP variability was associated with home BP, alcohol intake or sedentary lifestyle. Whether modifying these factors would reduce BP variability and whether such reduction would lead to better outcomes needs further study.