Stopping aspirin when on a blood thinner lowers risk of bleeding, study finds

Sept. 20, 2022
Talk to your doctor about whether taking aspirin can do you more harm than good.

If you’re already taking one blood thinner, mounting research suggests you might not need to take a second one.

In fact, when patients who are on a commonly prescribed blood thinner stop taking aspirin, their risk of bleeding complications drops significantly, a Michigan Medicine study finds.

Researchers analyzed over 6,700 people treated at anticoagulation clinics across Michigan for venous thromboembolism, or blood clots, as well as atrial fibrillation, an irregular heart rhythm that can cause stroke. Patients were treated with the common blood thinner warfarin but also took aspirin despite not having history of heart disease.

Over the course of the study intervention, aspirin use among patients decreased by 46.6%. With aspirin used less commonly, the risk of a bleeding complication dropped by 32.3% — amounting to one major bleeding event prevented per every 1,000 patients who stop taking aspirin. Results are published in JAMA Network Open.

This de-escalation of aspirin use is based off several studies that found concerning links between concurrent use of aspirin and different blood thinners.

One study reported that patients taking warfarin and aspirin for atrial fibrillation and VTE experienced more major bleeding events and had more ER visits for bleeding than those taking warfarin alone. Similar results occurred for patients taking aspirin and direct oral anticoagulants – who were found more likely to have a bleeding event but not less likely to have a blood clot.

For some people, aspirin can be lifesaving. Many patients who have a history of ischemic stroke, heart attack or a stent placed in the heart to improve blood flow – as well as those with a history of cardiovascular disease – benefit from the medication.

U of M Health release