Aspirin, often touted as a cheap effective medicine for heart patients, may only be of real benefit to those who have lower systolic blood pressure (SBP). Even so, it is not clear if the potential benefits outweigh the hazards of aspirin therapy.

GPs working with the Medical Research Council in London set out to determine which groups of patients derived the most benefit from low dose aspirin therapy for primary prevention of coronary heart disease (CHD). They studied nearly 5500 men, aged 45 to 69, who were deemed to be at increased risk of CHD. The men were randomly assigned to receive the anticoagulant warfarin, aspirin or placebo.

Results showed that aspirin did indeed reduce coronary events by 20 per cent. However, the greatest benefit was for non fatal events in those with low SBP. The relative risk of a non fatal heart event for aspirin takers with high SBP was nearly twice that of aspirin takers with low SBP.

Men with higher blood pressure given aspirin therapy, note the authors, are more prone to troublesome and occasionally serious non cerebral bleeding without any of the benefits in terms of reductions in coronary events and stroke, even with as little as 75 mg of aspirin daily (BMJ, 2000; 321: 13-7).