Patients taking long-term warfarin who decrease ‘inappropriate’ use of aspirin could benefit from improved clinical outcomes, suggest findings of a large-scale study in the US.

Researchers observed a significant reduction in major bleeding events but no increase in thrombotic outcomes when aspirin use was de-escalated in patients taking warfarin without an apparent indication for concomitant aspirin treatment.

“These findings highlight the need for greater aspirin stewardship among patients receiving warfarin for anticoagulation,” they said, in a paper published in JAMA Network Open.

The 10-year study involved 6,738 people treated for venous thromboembolism and atrial fibrillation with warfarin, who were also taking aspirin despite not having a history of heart disease.

Aspirin was discontinued with the approval of the managing clinician, and outcomes of aspirin use, bleeding and thrombosis were assessed both before and after this intervention.

Results showed that aspirin use among patients dropped 46.6%, while the risk of bleeding decreased by 32.3%, equating to 1 major bleeding event prevented for every 1,000 patients stopping aspirin.

“However, without a control group, it was not possible to know whether the intervention directly resulted in reduced bleeding outcomes,” the authors cautioned.

The researchers did not find a statistically significant difference in the mean percentage of patients having any post-intervention bleeding event (2.2% vs 1.3%, respectively), a non-major bleeding event (1.9% vs 1.1%), an emergency department visit for bleeding (0.94 vs 0.57); or percentage of patients admitted for bleeding (0.58% vs 0.35%), though here these results might have been limited by the length of follow-up affecting statical power, the investigators noted.

Crucially, there was no change in the mean percentage of patients having a thrombotic event following the aspirin reducing intervention, which indicates that its benefit of less major bleeds can be achieved without compromising the level of anticoagulant effect.

“With each study, we are seeing that there are far fewer cases in which patients who are already on an anticoagulant are seeing benefit by adding aspirin on top of that treatment,” noted Dr Geoffrey Barnes, senior author of the study and a cardiologist at the University of Michigan Health Frankel Cardiovascular Center.

“It’s really important for physicians and health systems to be more cognisant about when patients on a blood thinner should and should not be using aspirin.”