Introduction

Overwhelming evidence supports the concept that blood pressure in the population is a continuously distributed variable, bearing a graded relationship to risk of vascular events, so that any definition of hypertension is, by necessity, arbitrary. The line dividing ‘normal’ from ‘high’ blood pressures is often set at 140/ 90 mmHg, although definitions vary. By most criteria, approximately 10-20% of adults will develop raised levels of blood pressure by the time they are middle-aged.