Six studies with a total of 911,009 participants were included: one clinical trial, two cohort studies and three case-control studies.
Prevention of AMI (2 studies).
One all male clinical trial found a protective effect of aspirin (OR 0.58, 95% CI: 0.47, 0.72), while one all female cohort study found no effect (OR 1.18, 95% CI: 0.90, 1.55). When combining these two studies, only the fixed-effect model was significant (OR 0.75, 95% CI: 0.64, 0.88).
Cardiovascular mortality (4 studies).
The all male clinical trial and the all female cohort study showed no protective effect of aspirin. A large cohort study and a case-control study showed a protective effect. Overall, only the fixed-effect model was significant (OR=0.61, 95% CI: 0.59, 0.64).
All-cause mortality (2 studies).
The all male clinical trial showed no significant effect of aspirin, but the all female cohort study showed an increase in mortality (OR 1.51, 95% CI: 1.25, 1.82). Overall, the fixed-effect model showed increased mortality (OR 1.20, 95% CI: 1.05, 1.37).
Acute coronary syndromes (2 studies).
Two case-control studies found a protective effect of aspirin (OR 0.34, 95% CI: 0.26, 0.45).