Primary prevention of cardiovascular events with
aspirin in patients with elevated cardiovascular risk, including diabetics, is currently under intense discussion. Data from meta-analyses suggests that the efficacy of
aspirin in these patients is low, whereas there is a significantly increased
bleeding tendency. However, meta-analyses are based on trials that differ in many important aspects, including study selection. Fresh insights were expected from the ASCEND trial, by far the largest primary, randomized, placebo-controlled prevention trial in diabetics without known
cardiovascular disease. There was a small but significant reduction in serious cardiovascular events by
aspirin (8.6% vs. 9.6%) but also a significant increase in major
bleeding: 4.1% versus 3.2%. Unfortunately, this trial did not meet the desired annual rate of elevated vascular risk of ≥ 2%. It was only 1.2 to 1.3%, and thus in the range of other primary prevention trials in low-risk patients. Apart from potential compliance problems, possible explanations for the small cardioprotective effect of antiplatelet treatment include a healthy lifestyle as well as improved vascular protection by comedication with vasoactive and anti-inflammatory drugs, such as
statins or
antihypertensive agents, as well as
proton-pump inhibitors that might modify
bleeding, specifically in the upper gastrointestinal tract-the most frequently affected site. Also, the introduction of new
antidiabetic drugs with more favorable cardiovascular effects may in part explain the low event rate. ASCEND, similar to ARRIVE, did not study patients at elevated (as planned) but only at low vascular risk and, therefore, was largely confirmatory of earlier primary prevention trials.