Aims: The role of aspirin in the primary prevention setting is continuously evolving. Recent randomized trials have challenged the role of aspirin in the primary prevention setting.

Methods and results: Electronic databases were searched for randomized trials that compared aspirin vs. placebo (or control) in subjects without established atherosclerotic disease. The primary efficacy outcome was all-cause mortality, while the primary safety outcome was major bleeding. Summary estimates were reported using a DerSimonian and Laird random effects model. A total of 11 trials with 157 248 subjects were included. At a mean follow-up of 6.6 years, aspirin was not associated with a lower incidence of all-cause mortality [risk ratio (RR) 0.98, 95% confidence interval (CI) 0.93-1.02; P = 0.30]; however, aspirin was associated with an increased incidence of major bleeding (RR 1.47, 95% CI 1.31-1.65; P < 0.0001) and intracranial haemorrhage (RR 1.33, 95% CI 1.13-1.58; P = 0.001). A similar effect on all-cause mortality and major bleeding was demonstrated in diabetic and high cardiovascular risk patients (i.e. 10-year risk >7.5%). Aspirin was associated with a lower incidence of myocardial infarction (RR 0.82, 95% CI 0.71-0.94; P = 0.006); however, this outcome was characterized by considerable heterogeneity (I2 = 67%), and this effect was no longer evident upon limiting the analysis to the more recent trials. Trial sequential analysis confirmed the lack of benefit of aspirin for all-cause mortality up to a relative risk reduction of 5%.

Conclusion: Among adults without established cardiovascular disease, aspirin was not associated with a reduction in the incidence of all-cause mortality; however, it was associated with an increased incidence of major bleeding. The routine use of aspirin for primary prevention needs to be reconsidered.