Ed: Aspirin, once considered the “wonder drug” for its “proven clinical benefits and cheapness”, has come under close scrutiny in recent years.
There is no controversy in secondary cardiovascular prevention. Aspirin (or alternative antiplatelet agent) remains indicated for all patients with clinical cardiovascular disease (CHD, P.A.D, and ischaemic cerebrovascular disease).
In contrast, Aspirin in primary prevention is now being significantly challenged. In 2018 three large quality trials of Aspirin versus placebo in high risk primary prevention patients showed no net benefit. Whilst a modest reduction in cardiovascular events was observed, that benefit was balanced by an increased risk of serious bleeding with no net mortality benefit.
A meta-analysis published this year of 157,248 patients across 11 trials showed no net benefit for Aspirin over placebo for mortality, cardiovascular mortality or stroke risk. There was an 18% reduction in MI risk, but with a 47% increased risk of major bleeding and 33% increased risk of intracranial haemorrhage.
The cardiovascular benefits of Aspirin seen in earlier studies may also be lost if patients are on statins (and appropriate lifestyle changes). Aspirin should not be considered routinely for primary prevention. It may have a place in very high risk patients with documented atherosclerotic disease who haven’t had symptoms or a clinical event and who are at low bleeding risk. This requires careful case by case clinical judgement, as it remains unproven.
There are no randomised trials of Aspirin based on results of calcium scoring. Recent Australian NHF / CSANZ Guidelines for coronary calcium scoring have made recommendations based on extrapolation of risk, suggesting that Aspirin be considered in patients with calcium scores above 400, or scores between 100 and 400 that fall above the 75th percentile for age. Those recommendations have not considered the large recent negative trials of Aspirin so again adopt a case by case decision based on clinical judgement.
Despite evidence from early AF trials suggesting benefit, recent analyses indicate little or no benefit from Aspirin in high risk patients for thromboembolic prevention. Furthermore, bleeding risks associated with Aspirin appear to be nearly as high as the risk on NOACS. Thus, recent guidelines recommend no current role for Aspirin in AF.
Some studies have indicated a reduced colorectal cancer risk associated with Aspirin. Except for one study showing benefit in patients with Lynch syndrome with high genetic cancer risk, no large randomised trials in lower risk patients are published, so evidence is not conclusive. It can be considered for colorectal cancer prevention, on an individualised basis, in patients 50-70 years, with at least 10% ten year risk of cardiovascular event, low bleeding risk, willing to take daily Aspirin for at least 5-10 years.
- No routine place for Aspirin in primary prevention.
- Aspirin remains indicated for secondary prevention.
- No role for Aspirin in atrial fibrillation.
References available on request.
Questions? Contact the editor.
Author competing interests: nil relevant disclosures.
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