Using aspirin for primary prevention: The benefits and risks

Using daily aspirin treatment for the primary prevention of cardiovascular events remains an individualized decision that needs to balance a person’s risks for ischemic events and bleeding, according to results from a new systematic review of 15 randomized, aspirin-prevention trials, including results from three major trials that researchers reported during 2018.

“The findings suggest that the decision to use aspirin for primary prevention should be tailored to the individual patients based on estimated atherosclerotic cardiovascular disease risk and perceived bleeding risk, as well as patient preferences regarding the types of event prevented versus potential bleeding caused.”

The authors also concluded that if a person decides to use aspirin for primary prevention, then a low dose of 100 mg/day or less is recommended.

This new systematic review follows two reviews published earlier in 2019 that reached roughly similar conclusions after analyzing largely the same randomized trial data, including the same three major trials from 2018. One of these prior reviews included data from 13 trials and a total of 164,225 people. The second review had data from 11 trials with 157,248 people. The newly published review used data collected by 15 trials from 165,502 people.

The three 2018 trials that triggered the updated data assessments were the ARRIVE trial, with 12,546 people randomized the ASPREE trial, with 19,114 people randomized; and the ASCEND trial, with 15,480 people randomized.

As stated in the new report from a professor of medicine, and his associates, the recent trial results from 2018 added new data from more than 45,000 additional subjects, a development that warranted a reappraisal of the evidence for aspirin’s efficacy and safety for primary prevention in contemporary practice.

The major findings from the analysis by the group were that, in adults without a history of cardiovascular disease, daily aspirin use reduced the incidence of MIs, with a number needed to treat (NNT) of 357; reduced ischemic stroke (NNT, 500), reduced transient ischemic attack (NNT, 370), and reduced the overall, combined rate of all major adverse cardiovascular events (NNT, 263).

But on the safety side, daily aspirin led to an increased rate of major bleeding episodes, with a number needed to harm (NNH) of 222, increased intracranial bleeds (NNH, 1,000), and an increase in gastrointestinal bleeds (NNH, 385).

The analysis “demonstrates a potential reduction of net benefit with aspirin in the contemporary era.” They also noted that the benefits from aspirin prevention were, as expected, “more pronounced” among people with a higher estimated risk from atherosclerotic cardiovascular disease.

The systematic review findings came against the backdrop of a recently released primary prevention guideline. The guideline said that aspirin prophylaxis for primary prevention “might be considered” for adults aged 40-70 years, but should not be used for people who are older than 70, and also should not be given to people with an increased risk for bleeding. In general, the experts who produced this guideline said that aspirin prophylaxis should be infrequent.

The new analysis also found no reduction in the incidence of cancer or cancer-related death linked with aspirin use for primary prevention. The systematic review published earlier in 2019 also found no link between aspirin use and cancer incidence or mortality.