The potential cardiovascular benefits of aspirin are outweighed by the risk of nontrivial bleeding in people without cardiovascular disease (CVD), a meta-analysis has shown.

The researchers analysed nine randomised placebo-controlled trials reporting on cardiovascular disease, non-vascular outcomes or death. Each trial contained at least 1,000 participants, mean age at baseline was 57 years and 46% of participants were men.

Study-specific odds ratios (OR) were combined using random effects meta-analysis. The risk profile of aspirin was evaluated by comparing CVD risk reductions with increases in bleeding.

Mean follow-up was six years. Aspirin treatment reduced total cardiovascular events by 10%, OR 0.90 (95% CI: 0.85-0.96) mainly through a reduction in non-fatal MI OR 0.80 (95% CI: 0.67-0.96). There was no significant reduction in CVD mortality OR 0.99 (95% CI: 0.85-1.15) or cancer deaths OR 0.93 (95% CI: 0.84-1.03).

However, there was a 30% increased risk of nontrivial bleeding events OR 1.31 (95% CI: 1.14-1.50). The number needed to treat to prevent one cardiovascular event was 120, compared with the number needed to harm of 73 for causing a bleed.

The controversy over aspirin continues. Previous studies had suggested that healthy people who take regular aspirin have a reduced risk of both CVD and cancer. Others, however, have argued that the risk of bleeding is not to be ignored and the benefits do not justify the use of aspirin in primary prevention.

The authors of this meta-analysis conclude that despite important reductions in non-fatal MI, aspirin prophylaxis in people without prior CVD does not lead to a reduction in either cardiovascular deaths or cancer mortality. They point out that any benefits are offset by clinically important bleeding events and as such the routine use of aspirin for primary prevention cannot be recommended. Treatment decisions need to be considered on a case by case basis, they say.

The reality of this study for primary care physicians is that whatever level of cardiovascular risk a patient is at, the bleeding risk with aspirin primary prevention is always greater than the cardiovascular benefits. Therefore the focus of such primary prevention should be on diet, exercise, smoking, cholesterol and blood pressure.

Dr Peter Savill

• Seshasai SRK, Wijesuriya S, Sivakumaran R et al. Effect of aspirin on vascular and non-vascular outcomes: meta-analysis of randomized controlled trials. Arch Intern Med 2012; 172(3):209-216