= Registered users
= Paid-up subscribersAnother study has cast doubt on the role of aspirin in primary prevention. The Aspirin for Asymptomatic Atherosclerosis trial showed no reduction in vascular events with aspirin in asymptomatic subjects with a low ankle brachial index (ABI).
Men and women aged 50-75 years living in central Scotland were invited for ABI screening for asymptomatic atherosclerosis over a ten-year period from 1998 to 2008. A total of 28,980 patients were screened of which 3,350 had a low ABI and were randomised to aspirin 100mg or placebo. Patients were followed up for a mean of 8.2 years.
The primary end point was a composite of an initial fatal or nonfatal coronary event, stroke, or revascularisation. Secondary end points were all vascular events (including angina, intermittent claudication and transient ischaemic attack) and all-cause mortality.
The results showed no difference in outcome with aspirin for either primary or secondary end points: primary end point hazard ratio 1.03 (95% CI: 0.84-1.27); vascular events
HR 1.0 (95% CI: 0.85-1.17); all cause mortality HR 0.95 (95% CI 0.77-1.16). However, there was a greater incidence of adverse events in the aspirin group - major haemorrhage HR 1.71 (95% CI: 0.99-2.97).
The use of aspirin for the primary prevention of cardiovascular disease has recently come under some scrutiny.
There is little doubt that aspirin is beneficial in patients with symptomatic cardiovascular disease or with a history of stroke but this trial adds further weight to the reluctance to use aspirin for primary prevention in asymptomatic patients even in those considered at high risk with little evidence of benefit and some evidence of harm.
However, compliance over the course of the study was only 60% which may have limited the ability of aspirin to show a clear benefit although that sort of figure is probably not atypical of a real life situation when using aspirin in this context. Furthermore the incidence of bleeding would be expected to be higher with better compliance. Finally the ABI cut off of <0.95 may have been too high to identify a truly high-risk population.
Dr Peter Savill