Gastrointestinal bleeding is a common side effect for many blood-thinning medications. But new Mayo Clinic research finds that risk is amplified when patients receive more than one blood thinner – especially if they’re 75 or older.

The study, published in Clinical Gastroenterology and Hepatology, found patients receiving an anticoagulant drug and an antiplatelet drug, in combination, were at a significantly higher risk of gastrointestinal bleeding. Anticoagulant drugs (such as warfarin and apixaban) slow down blood clotting, while antiplatelets (such as aspirin and clopidogrel) prevent platelets from clumping. Both types of blood thinners are commonly used to prevent strokes in patients with heart conditions.

“Most of the literature on bleeding risks for blood-thinning medications compares one medication to another, or focuses on patients with one condition,” says lead author Neena Abraham, M.D., a Mayo Clinic gastroenterologist, and site director in Arizona for health care delivery research in the Mayo Clinic Robert D. and Patricia E. Kern Center for the Science of Health Care Delivery. “By not limiting our investigation to one cardiovascular group, we were successful in demonstrating the magnitude of risk of all commonly prescribed antiplatelet and anticoagulant regimens among a broad range of cardiovascular patients.”

The Mayo team of researchers and physicians analyzed 311,211 patients receiving blood-thinning medication between Oct. 1, 2010, and May 31, 2017, using the OptumLabs Data Warehouse — a longitudinal, real-world data asset with de-identified administrative claims and electronic health record data.  

After one year, patients being treated for both atrial fibrillation and coronary artery disease, for example, had a similar risk of bleeding (4 percent) when getting just an anticoagulant or just an antiplatelet, but a 7.4 percent risk when receiving both. Only 29 patients with atrial fibrillation and coronary artery disease would need to be treated with an anticoagulant and antiplatelet in combination to cause one additional bleeding event, according to the study. The researchers say it’s important for physicians to be aware of the increased risk; patients with both of these conditions received a combination of blood thinners 56.8 percent of the time.

The study also found that patients 75 and older were twice as likely as younger patients to have gastrointestinal bleeding when on two blood thinners. Patients were at a similar risk for bleeding when using just an anticoagulant or just an antiplatelet drug, the researchers say.

“Many providers assume that antiplatelets may be safer compared to anticoagulants for patients at moderate-to-high bleeding risks,” Dr. Abraham says. “However, this study demonstrates that these risks may be similar – an important consideration as providers decide on optimal treatment strategies.”

Study co-investigators are Nilay Shah, Ph.D., Peter Noseworthy, M.D., Jonathan Inselman, Xiaoxi Yao, Ph.D., Lindsey Sangaralingham, Gabriella Cornish, and Che Ngufor, Ph.D., all Mayo Clinic, and Jeph Herrin, Ph.D., Yale School of Medicine.

The research was funded by a grant from the Agency for Healthcare Research and Quality, for which Dr. Abraham is the principal investigator.

All Mayo Clinic investigators on this project are affiliated with the Mayo Clinic Robert D. and Patricia E. Kern Center for the Science of Health Care Delivery. Center research focuses on transforming clinical practice. Researchers seek to discover new ways to improve health; translate those discoveries into evidence-based, actionable treatments, processes and procedures; and apply this new knowledge to improve patient care.

About OptumLabs
OptumLabs is a collaborative center for research and innovation co-founded by Optum and Mayo Clinic, and focused on improving patient care and patient value. The OptumLabs Data Warehouse is a longitudinal, real-world data asset with de-identified administrative claims and electronic health record data.

The Mayo Clinic Robert D. and Patricia E. Kern Center for the Science of Health Care Delivery, which leads the relationship with OptumLabs for Mayo Clinic, has published a number of studies identifying areas for potential improvements in health care delivery using the OptumLabs Data Warehouse.

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