Abstract 4194: Low-Dose Aspirin Reduces Cardiovascular Events and All-Cause Mortality Among Patients with Stable Cardiovascular Disease: A Meta-Analysis

Abstract

Background: The Antithrombotic Trialists’ Collaboration meta-analysis demonstrated that anti-platelet therapy reduced cardiovascular events in patients with prior cardiovascular disease. However, in that analysis, stable and unstable patients were grouped together, all anti-platelet agents were combined and most of the aspirin studies used a dose higher than currently recommended (>325mg/day). The effect of low-dose aspirin (50–325mg/day) in patients with stable cardiovascular disease has not been reported. Methods: Secondary prevention trials of low-dose aspirin in patients with stable cardiovascular disease were identified by searches of the MEDLINE database from 1966 to 2006. Six randomized trials were identified that enrolled patients with a history of myocardial infarction (n=1), stable angina (n=1) and a stroke or transient ischemic attack (n=4). A random effects model was used to combine results from individual trials. Results: The 6 studies randomized a total of 9,853 patients. Aspirin therapy was associated with a significant 21% reduction in the risk of cardiovascular events (non-fatal MI, non-fatal stroke and cardiovascular death) (Odds Ratio (OR) 0.79, 95% Confidence Interval (CI) 0.72– 0.88, P<0.01), 26% reduction in the risk of non-fatal MI (OR, 0.74, 95% CI, 0.60– 0.91, P<0.01), 25% reduction in the risk of stroke (OR, 0.75, 95% CI, 0.65– 0.87, P<0.01) and a 13% reduction in the risk of all-cause mortality (OR, 0.87, 95% CI, 0.76– 0.98, P=0.03).Based on these data, treatment of 30 patients with low-dose aspirin is required to prevent 1 cardiovascular event, 83 patients to prevent 1 non-fatal MI, 40 patients to prevent 1 stroke and 71 patients to prevent 1 death. Patients treated with aspirin were significantly more likely to experience severe bleeding (OR, 2.2, 95% CI, 1.4–3.4, P<0.01). The number needed to harm from severe bleeding is 111 patients. Conclusion: Among patients with stable cardiovascular disease, low-dose aspirin therapy reduces the incidence of adverse cardiovascular events and all-cause mortality, while increasing the risk of severe bleeding. The protective effect of aspirin supports current recommendations that all patients with stable cardiovascular disease be placed on low-dose aspirin.