Repeated evening home blood pressure measurement improves prognostic significance for stroke: a 12-year follow-up of the Ohasama study

OBJECTIVE: To compare the predictive power of home blood pressure (HBP) measured in the evening (E-HBP) and that of casual screening BP (CBP) for stroke risk in relation to the number of E-HBP measurements. METHODS: We obtained E-HBP (measured once in the evening just before going to bed for 4 weeks) and CBP (measured twice during the health checkup) from 2234 Japanese participants aged >or=35 years who had no history of a previous stroke. The participants were followed-up for a median duration of 11.9 years. The multivariate adjusted relative hazard (RH) and 95% confidence intervals (CI) for each 10 mmHg (systolic) or 5 mmHg (diastolic) increase in BP was determined by Cox regression model. RESULTS: There were 226 incidences of stroke. Even the initial E-HBP values significantly predicted future stroke events (systolic RH=1.19, 95% CI=1.11-1.28; diastolic RH=1.12, 95% CI=1.06-1.19), and the predictive power of E-HBP increased progressively with the increased number of measurements. When initial systolic E-HBP and systolic CBP values were simultaneously included into the Cox model, only initial E-HBP was significantly related with stroke risk (E-HBP RH=1.17, 95% CI=1.08-1.26; CBP RH=1.07, 95% CI=0.99-1.15). CONCLUSION: E-HBP has a stronger predictive power than CBP regardless of the number of measurements. Our findings emphasize the important clinical significance of E-HBP over CBP, even though the measurement conditions of E-HBP are generally less strict than that of morning HBP measurements.