The effects of antihypertensive drug treatment on the incidence of stroke and of coronary heart disease

The effects of differences in usual diastolic blood pressure (DBP) on the risks of stroke and of coronary heart disease (CHD) were estimated from nine major prospective observational studies involving about 420,000 men and women, followed up over intervals of 6 to 25 years. The results indicated that a prolonged difference in usual DBP of approximately 6 mmHg was associated with about 36% (±2) fewer strokes and 22% (±1) fewer CHD deaths and non-fatal myocardial infarctions. The effects of equivalent reductions in DBP produced by antihypertensive drug treatment but maintained for just a few years, have been estimated in several overviews of randomised controlled trials, involving totals of between 30,000 and 40,000 hypertensive patients. The results of the overviews indicated that antihypertensive treatment reduced the risk of stroke by about 40% suggesting that all of the long-term potential benefit for stroke of lower DBP was achieved within about 3 years of beginning treatment. The risk of CHD may have been reduced by about 10% among patients allocated active treatment, but the 95% confidence limits for the difference ranged from about zero to about 20% Whatever the true effect of treatment on CHD, it would appear to be somewhat less than the difference in risk estimated from the prospective observational studies for a prolonged difference in DBP of the same size. This apparent shortfall may reflect chronic pathophysiological processes in the relationship between DBP and CHD, and/or possible cardiotoxic side-effects of the principal trial treatments. © 1989 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted.