Background:

The usefulness of aspirin in primary prevention continues to be the subject of debate. Medical advances and the variability of cardiovascular risk could explain the heterogeneity of the published studies. High risk populations would have greater benefit.

Objective:

Analyzing the effects of aspirin in patients without cardiovascular disease and evaluating the results according to the cardiovascular risk of the populations.

Methods:

Studies evaluating aspirin versus placebo in primary prevention were included. The primary endpoint was the combined cardiovascular death, acute myocardial infarction (AMI) and ischemic stroke. The final safety point was the combination of hemorrhagic stroke and major bleeding. The studies were classified into low and moderate/high risk, according to the number of events in the placebo arm.

Results:

Thirteen studies were evaluated (n = 164,225), eight of low cardiovascular risk (n = 118,455) and five of moderate/high risk (n = 45,770). There was a reduction of the combined endpoint in the aspirin group (odds ratio [OR] 0.90; 95% confidence interval [CI], 0.85-0.94), without differences in cardiovascular mortality (OR 0.94; 95% CI, 0.86-1.04). No differences were observed when comparing the risk subgroups. Greater hemorrhagic complications were observed in the aspirin group (OR 1.45; 95% CI, 1.32-1.60), without differences between the risk subgroups.

Conclusion:

Aspirin was associated with a slight decrease in AMI and ischemic stroke in absolute terms, with no differences in cardiovascular mortality. This accompanied by the increase in hemorrhagic complications, results in an absence of net clinical benefit. The baseline cardiovascular risk of the population did not affect the results.