Six RCTs (n=95,456) were included. Three studies included only males, one included only females and two included both sexes.
Aspirin was associated with a statistically significant decrease in cardiovascular events in women (OR 0.88, 95% CI: 0.79, 0.99, P=0.03) and men (OR 0.86, 95% CI: 0.78, 0.94, P=0.01) compared with placebo.
In women, aspirin was associated with a statistically significant reduction in the occurrence of stroke (OR 0.83, 95% CI: 0.70, 0.97, P=0.02). When stroke sub-type was investigated, aspirin was associated with a reduction in ischaemic stroke but not haemorrhagic stroke. There was no statistically significant effect on MI, cardiovascular and all-cause mortality for women.
In men, aspirin was associated with a statistically significant reduction in the occurrence of MI (OR 0.68, 95% CI: 0.54, 0.86, P<0.001), but had no statistically significant effect on stroke overall (though there was a statistically significant increase in haemorrhagic stroke) and no effect on cardiovascular and all-cause mortality.
Aspirin therapy increased the risk of bleeding in both men and women.
No evidence of publication bias or statistically significant heterogeneity was found.