Abstract

INTRODUCTION

Blood pressure is the single most important modifiable risk factor for stroke. Key epidemiological data about the relationship between blood pressure and stroke come from both prospective observational (cohort) studies and randomised controlled trials. Cohort studies provide information about the effects of prolonged blood pressure differences between groups of people (MacMahon et al. 1990), while clinical trials provide evidence about the effects of short-term reductions in blood pressure (Collins et al. 1990). Cohort studies in both Western (Prospective Studies Collaboration 1995) and Eastern (Eastern Stroke and Coronary Heart Disease Collaborative Research Group 1998; Asia Pacific Cohort Studies Collaboration 1999) populations have established a strong and direct association between the risk of first-ever stroke and level of blood pressure, with no detectable lower level of blood pressure below which the risk of stroke does not continue to decline (Fig. 1). A similar association is evident among patients who have had