The quality of evidence is downgraded by inconsistency (unexplained variability in results).
The ASCEND study 4 included 15 480 patients with diabetes (94% type 2 diabetes) but no evident cardiovascular disease. Majority of participants had statins and blood pressure-lowering therapy. They were randomized to receive aspirin at a dose of 100 mg daily or matching placebo. The primary efficacy outcome was the first serious vascular event (i.e., myocardial infarction, stroke or transient ischemic attack, or death from any vascular cause, excluding any confirmed intracranial hemorrhage). During a mean follow-up of 7.4 years, there were less serious vascular events in the aspirin group than in the placebo group (658 participants [8.5%] vs. 743 [9.6%]; rate ratio, 0.88, 95% CI 0.79 to 0.97; P=0.01). In contrast, major bleeding events occurred in 314 participants (4.1%) in the aspirin group, as compared with 245 (3.2%) in the placebo group (RR 1.29, 95% CI 1.09 to 1.52; P=0.003), with most of the excess being gastrointestinal bleeding and other extracranial bleeding. The absolute benefits were largely counterbalanced by the bleeding hazard (91 patients would need to be treated to avoid a serious vascular event over a period of 7.4 years, and 112 to cause a major bleeding event). There was no significant difference between the aspirin group and the placebo group in the incidence of gastrointestinal tract cancer (secondary outcome) (157 participants [2.0%] and 158 [2.0%], respectively) or all cancers (897 [11.6%] and 887 [11.5%]).
The PPP (Primary Prevention Project) trial 2 included a subgroup of 1031 people with diabetes aged>/=50 years and without a previous cardiovascular event. In diabetic patients, aspirin treatment was associated with a nonsignificant reduction in the main end point of cardiovascular death, stroke, or myocardial infarction (RR 0.90, 95% CI 0.50 to 1.62) and in total cardiovascular events (RR 0.89, 95% CI 0.62-1.26) and with a nonsignificant increase in cardiovascular deaths (RR 1.23, 95% CI 0.69 to 2.19). In nondiabetic subjects, RRs for the main end point, total cardiovascular events, and cardiovascular deaths were 0.59 (0.37-0.94), 0.69 (0.53-0.90), and 0.32 (0.14-0.72), respectively.
The meta-analysis of the Antithrombotic Trialists' Collaboration 3 on the efficacy of antiplatelet therapy in the prevention of major cardiovascular events in high risk patients (with acute or previous vascular disease or some other predisposing condition) showed a clear benefit for the entire population of more than 140 000 patients (reduction of the combined outcome of any serious vascular event by about one quarter)Antiplatelet Therapy for Prevention of Death, Myocardial Infarction, and Stroke, but no statistically significant benefit was documented in the subgroup of about 5000 diabetic patients (7% risk reduction).
A subgroup analysis 5 of a RCT evaluating two doses of aspirin widely used for secondary prevention included 15 076 patients with ASCVD. 5 676 (39%) had DM of whom 2 820 were assigned to 81 mg aspirin and 2 856 to 325 mg aspirin. Patients with vs. without DM had higher rates of the composite cardiovascular outcome (9.6% vs. 5.9%; P < 0.001) and bleeding events (0.78% vs. 0.50%; P < 0.001). When comparing the doses, patients with DM had no difference in the primary effectiveness outcome (9.3% vs. 10.0%; hazard ratio [HR] 0.98, 95% CI 0.83 to 1.16; P = 0.265) or safety outcome (0.87% vs. 0.69%; subdistribution HR 1.25, 95% CI 0.72 to 2.16; P = 0.772).
The following decision support rules contain links to this evidence summary:
Primary/Secondary Keywords