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Aspirin can block the aggregation of blood platelets and in the early 1980s several randomised trials assessed whether it might be able to prevent heart attacks and strokes in people at high risk of such an event. These trials were too small to provide a definitive answer, so we established the Anti-Platelet Trialists’ (APT) Collaboration to conduct a meta-analysis of all such trials.

Aspirin tablets.

The Anti-Platelet Trialists’ (APT) Collaboration found that a prolonged course of aspirin or some other antiplatelet drug reduced the risk of a heart attack, stroke or death from vascular disease by about one quarter. Since then many trials have explored the effects of antiplatelet drugs in a wide range of patients, and the APT Collaboration (now known as the Anti-Thrombotic (ATT) Collaboration) has produced updates to worldwide evidence from trials to provide clinicians with reliable information about these drugs (e.g. in papers published in 1994 and 2002). In 2009 the ATT showed that aspirin was not of clear net benefit for the primary prevention of vascular disease among apparently healthy people.

The Clinical Trial Service Unit and Epidemiological Studies Unit (CTSU) has conducted randomised trials of aspirin, including the 17,000 patient Second International Study of Infarct Survival (ISIS-2), published in 1988. This study showed that starting a 5-week course of aspirin soon after symptoms of a heart attack reduced the risk of death by about one quarter. Other antiplatelet trials include the Chinese Acute Stroke Trial (CAST) and CCS-2 (pdf), which both showed the effectiveness of antiplatelet regimens after acute stroke among Chinese patients.

The results of CTSU's ASCEND trial of aspirin versus placebo among around 15,000 patients with diabetes and no prior history of vascular disease were announced in 2018.

Research groups working in this area