Prediction of stroke by ambulatory blood pressure monitoring versus screening blood pressure measurements in a general population: the Ohasama study

Objective To investigate the association between 24 h, daytime and night-ti me ambulatory blood pressures and first symptomatic stroke, to compare thei r predictive powers for stroke with that of casual (screening) blood pressu re, and to compare the predictive power for stroke between daytime and nigh t-time blood pressures, in a general population in Ohasama, Japan. Design A prospective cohort study. Subjects and methods We obtained ambulatory blood pressure on 1464 subjects aged greater than or equal to 40 years without history of symptomatic stro ke, then followed-up their stroke-free survival. There were 74 first sympto matic stroke during the follow-up period (mean = 6.4 years). The prognostic significance of blood pressure for stroke risk was examined by a Cox propo rtional hazards regression model adjusted for possible confounding factors. Results The non-parametric and parametric analysis indicated that 24-h, day time and night-time ambulatory blood pressures were linearly related with s troke risk The likelihood ratio analysis demonstrated that these ambulatory blood pressures were significantly better related to stroke risk than did screening blood pressure, and that daytime blood pressure better predicted stroke risk than did night-time blood pressure. Conclusions The present study which prospectively investigated the relation between ambulatory blood pressure and first symptomatic stroke risk in a g eneral population demonstrated that (i) ambulatory blood pressure values we re linearly related to stroke risk; (ii) ambulatory blood pressures had the stronger predictive power for stroke risk than did screening blood pressur e; and (iii) daytime blood pressure better related to stroke risk than did night-time blood pressure. J Hypertens 2000, 18:847-854 (C) Lippincott Will iams & Wilkins.