NHS Evidence has published Eyes on Evidence for September 2011. This issue includes the results of a meta-analysis into the risks and benefits of aspirin treatment for the primary prevention of cardiovascular disease.
This most recent study was published in the American Heart Journal. Nine trials involving 102,621 patients that ran for an average of 6.9 years were reviewed. Aspirin treatment was associated with a reduction in the composite primary outcome of major cardiovascular events (risk ratio [RR] 0.90, 95% CI 0.85-0.96, P<0.001) but there was no significant reduction for the individual outcomes of myocardial infarction, stroke, ischaemic stroke or all-cause mortality.
Conversely, there was an increased risk of haemorrhagic stroke (RR 1.35, 95% CI 1.01-1.81, P=0.04) and major bleeding (RR 1.62, 95% CI 1.31-2.00, P<0.001).
The authors also summarise this data over a 5 year period noting that for every 1,000 patients treated aspirin would prevent 2.9 major cardiovascular events but cause 2.8 major bleeds.
The authors conclude that, "the evidence provides only modest support for a benefit of aspirin in patients without clinical cardiovascular disease, which is offset by its risk".
NHS Evidence also notes that current 'PolyPill' trials have explicitly not included aspirin in the studies, instead opting for a combination of statins and antihypertensive agents. It is also noted that secondary prevention is a different matter as aspirin is linked with a 15% reduction in subsequent events in such patients.
Action: Clinicians should be aware of UK policy to not use aspirin for primary prevention. Eyes on Evidence may also be a useful resource in maintaining up to date knowledge.
Thanks to Kevin Ashworth for spotting this article