Aspirin and other antiplatelet drugs
In the early 1980s several randomised trials had assessed whether aspirin, which can block the aggregation of blood platelets, might be able to prevent heart attacks and strokes in those at high risk of such an event. But they were too small to provide a definitive answer to this question, so CTSU established the Anti-Platelet Trialists’ (APT) Collaboration to conduct a meta-analysis of all such trials, which then established that a prolonged course of aspirin (or some other antiplatelet drug) reduced the risk of a serious vascular event (heart attack, stroke or death from vascular disease) by about one quarter. In the ensuing 3 decades 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 provided updates the worldwide evidence from trials (for example, in papers published in 1994 and again in 2002) to provide reliable information about such drugs to clinicians. In 2009 the ATT showed that aspirin was not of clear net benefit for the primary prevention of vascular disease among apparently healthy people.
CTSU has also conducted a number of its own randomised trials of aspirin. These include the 17,000 patient Second International Study of Infarct Survival (ISIS-2), published in 1988, which showed that a 5-week course of aspirin initiated soon after symptoms of a heart attack reduced the risk of death by about one quarter. Other antiplatelet trials have included the Chinese Acute Stroke Trial (CAST) and CCS-2, both of which showed the effectiveness of antiplatelet regimens after acute stroke among Chinese patients.
Currently, CTSU is conducting the ASCEND trial of aspirin versus placebo among around 15,000 patients with diabetes mellitus who do not have any prior history of vascular disease. Results from the trial are expected in 2018.