Taking low dose aspirin as a preventive measure against coronary heart disease, which is a very common practice, may actually cause more harm than good, according to a just published study.

British researchers identified over 5,000 UK men, aged between 45 and 69 years, who were at increased risk of coronary heart disease but had not previously had heart trouble. The men were randomly divided into four different treatment groups to accurately establish the effect of aspirin.

The authors found a greater beneficial effect of aspirin in men with low rather than high blood pressures, not only for coronary heart disease but also for stroke, although the modest benefit does not necessarily outweigh the risk of bleeding. Men with higher pressures may derive no protective benefit from aspirin but will risk possible serious bleeding.

Given the widespread use of aspirin for the prevention of coronary heart disease, the study's authors suggest that these findings have important implications, although they admit that further trials are needed to confirm the results.

Because of the strong correlation between blood pressure found in this study, the authors also stress the importance of adequately controlling blood pressure for those in whom the preventive use of aspirin is being considered. In addition, men who have previously had heart trouble and strokes and are taking aspirin should continue to do so, unless instructed otherwise, since they are more likely to obtain a greater benefit than the general population.

British Medical Journal June 25, 2000; 321: 13-17.