The Lancet has published the results of a meta-analysis that aimed to assess the benefits and risks of aspirin therapy in the primary prevention of vascular events. This study has been reported in the general media (BBC) and builds on previous analyses.
The analysis was conducted by the Antithrombotic Trialists' Collaboration and included data from six trials with 95,000 participants. Aspirin therapy produced a 12% relative risk reduction (absolute risk of 0·51% with aspirin versus 0·57% control per year) in serious vascular events mainly driven by reductions in non-fatal heart attacks. Aspirin treatment also increased major gastrointestinal and extra-cranial bleeds (0·10% versus 0·07% per year). These figures equate to a number needed to treat (NNT) of 1,667 for one year to prevent a serious vascular event compared to a number needed to harm (NNH) of 3,334 for major gastrointestinal and extra-cranial bleeds in the same time period.
The authors conclude that in primary prevention "aspirin is of uncertain net value as the reduction in occlusive events needs to be weighed against any increase in major bleeds". They also note that further research is under way.
Action: Clinicians should ensure that other modifiable risk factors (lifestyle, smoking, blood pressure, blood lipids) for cardiovascular events are managed appropriately in individuals who are identified as being at higher risk. Recommendation of aspirin therapy requires a careful consideration of the potential risks and benefits.