In the linked randomised controlled trial (doi:10.1136/bmj.a1840), Belch and colleagues assess whether aspirin and antioxidants, given together or separately, reduce cardiovascular events in patients with diabetes mellitus and asymptomatic peripheral arterial disease.1

The use of aspirin for secondary prevention of cardiovascular events in patients with coronary or cerebrovascular disease is well established and is based on extensive evidence from the Antithrombotic Trialists’ Collaboration.2 That meta-analysis found that aspirin was beneficial in patients with acute myocardial infarction or ischaemic stroke; unstable or stable angina; and those with previous myocardial infarction, stroke, or cerebral ischaemia. However, not all patients with cardiovascular disease respond to aspirin, as shown by a recent meta-analysis of aspirin trials in peripheral artery disease.3

In contrast, studies evaluating the possible benefits of aspirin for primary prevention in patients without cardiovascular disease have been consistently negative. A review by the United States Food and Drug Administration (FDA) of the proposed labelling of aspirin for primary prevention in 2003 evaluated five primary prevention trials and found that they were all negative for their primary end point.4 Further examination of those trials in the higher risk subgroups (Framingham risk score greater than 8-10% a decade) and in patients with diabetes also failed to show a benefit …