The association between early aspirin and decreased mortality was greater in patients older than 60 years (F statistic = 10.8; P for interaction = .001) and in patients with at least 1 comorbidity (F statistic = 20.2; P for interaction <.001). This was consistent after subgroup balancing, and patients receiving early aspirin between ages 18 and 40 years and 41 and 60 years did not have lower odds of mortality. However, patients between ages 61 and 80 years (OR, 0.79; 95% CI, 0.72-0.87; P < .001) and older than 80 years (OR, 0.79; 95% CI, 0.69-0.91; P < .001) receiving early aspirin had lower odds of mortality. In patients without comorbidities, there was no association between early aspirin and mortality (OR, 0.99; 95% CI, 0.80-1.23; P = .96), whereas in those with 1, 2, 3, and more than 3 comorbidities receiving early aspirin, there were lower odds of mortality (1 comorbidity: 6.4% vs 9.2%; OR, 0.68; 95% CI, 0.55-0.83; P < .001; 2 comorbidities: 10.5% vs 12.8%; OR, 0.80; 95% CI, 0.69-0.93; P = .003; 3 comorbidities: 13.8% vs 17.0%, OR, 0.78; 95% CI, 0.68-0.89; P < .001; >3 comorbidities: 17.0% vs 21.6%; OR, 0.74; 95% CI, 0.66-0.84; P < .001). (Figure 3).