Advice on aspirin and primary prevention

‘Aspirin for primary prevention: generally no, though occasionally yes’ is the aide-mémoire proposed by the authors of a recent Drug and Therapeutics Bulletin (DTB) review.

Unlike in secondary prevention, aspirin use to prevent first cardiovascular events has remained controversial. Three large studies conducted in 2018 failed to show significant benefit and, according to the DTB report authors, these studies have shifted the risk versus benefit balance of aspirin for primary prevention.

Using the 2018 data, the authors highlight an updated meta-analysis (13 studies; 164 225 participants) that suggests that aspirin use is associated with a reduction in the composite outcome of cardiovascular mortality, non-fatal myocardial infarction (MI) and non-fatal stroke (hazard ratio [HR], 0.89; absolute risk reduction, 0.41%; number needed to treat [nnt], 241).

However, there was also an increased risk of major bleeding events with aspirin (HR, 1.43; absolute risk increase, 0.47%; number needed to harm [NNH], 210) and an increased risk of intracranial haemorrhage (NNH, 927) and major gastrointestinal bleeding (NNH, 334).

The authors recommend that clinicians ensure other cardiovascular risk factors have been optimally controlled first before considering aspirin initiation (for example, smoking, cholesterol and blood pressure).

The authors suggest discussing what risk of bleeding the patient is prepared to accept to gain a small reduction in MI with aspirin. Patient’s bleeding risk factors (including the use of non-steroidal anti-inflammatory drugs, selective serotonin-reuptake inhibitors, corticosteroids and anticoagulants) should be assessed and, if any of these risk factors are present, the patient should be told that the likelihood of aspirin providing a net benefit for primary prevention is low; making aspirin hard to justify.

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