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New aspirin meta-analysis

The Archives of Internal Medicine has published the results of a new meta-analysis that aimed to assess the net benefit of aspirin in the primary prevention of cardiovascular disease. This study has also been reported in the general media (BBC).

This analysis included data for 102,621 participants from 9 studies that reported event rates for vascular and non-vascular outcomes as well as deaths. It was found that over a mean period of 6.0 years, treatment with aspirin resulted in a 10% reduction in cardiovascular events (OR 0.90, 95% CI 0.85-0.96, NNT = 120) although there was no reduction in cardiovascular deaths.

It was also noted that there was a 31% increase in serious bleeding events (OR 1.31 , 95% CI 1.14-1.50, NNH = 73).

The authors note that the benefits in non-fatal events are offset by clinically important bleeding events and conclude that, "routine use of aspirin for primary prevention is not warranted and treatment decisions need to be considered on a case-by-case basis".

Action: The conclusion of this paper is not new and it is already recommended that aspirin is not used for the primary prevention of cardiovascular events. The data on the event rates in this paper (including the NNT and NNH) may prove useful in communicating the risks and benefits to patients.