April 19 (UPI) -- More than one-third of people who have atrial fibrillation or blood clots are treated with both a blood-thinner and daily aspirin therapy, even when there is no clear need for the latter, a study published Monday by JAMA Internal Medicine found.
Those given the drugs at the same time had about a 25% higher risk for bleeding "events," or being unable to stop blood flow following an injury, and a roughly 40% increased likelihood of hospitalization for a related health problem, the data showed.
Meanwhile, patients who received both blood thinners and aspirin simultaneously have the same risk for blood clots as those on blood thinners alone.
"The patients on combination therapy were more likely to have bleeding events, but they weren't less likely to have a blood clot," study co-author Dr. Jordan Schaefer said in a press release.
"Therefore, it's important that patients ask their doctors if they should be taking aspirin when they are prescribed a direct oral [blood thinner]," said Schaefer, an assistant professor of internal medicine and a hematologist at Michigan Medicine in Ann Arbor.
Atrial fibrillation, or AFib, is an irregular heartbeat that can cause blood clots, stroke, heart failure and other heart-related health problems, according to the American Heart Association.
Nearly 3 million people in the United States have the condition, the association estimates.
Typically, people with AFib, or those who have suffered a severe clot -- a venous thromboembolism -- as a result of blood hardening and blocking a vein and reducing blood flow, are prescribed a blood thinner to prevent future clots, according to Schaeder and his colleagues.
Examples of blood thinners include apixaban, which is marketed under the brand name Eliquis; rivaroxaban, or Xarelto; and warfarin, or Coumadin.
Aspirin therapy also is recommended for some of these patients, such as those with a recent history of a heart attack or of having undergone heart valve replacement surgery, to prevent future heart attacks and strokes, Schaefer and his colleagues.
In these patients, aspirin can help improve blood flow because it works to limit the production of blood platelets, the researchers said.
The study of nearly 3,300 adults who take blood thinners for AFib or blood clots, but did not have a recent history of heart attack or heart valve replacement, found that more than 1,100, or 34%, also received daily aspirin.
The use of the two drugs together did not reduce patients' risk for blood clots, but they did raise their risk for bleeding events, according to the researchers.
The combination of a blood thinner and aspirin may be appropriate for people who have had a recent heart attack, recent coronary stent placement or bypass surgery, study co-author Dr. Geoffrey Barnes said.
However, for others, "combination therapy may not be happening intentionally [as] the addition of aspirin might get overlooked because it's not in any one specialist's ... territory," said Barnes, an assistant professor of internal medicine and a vascular cardiologist at Michigan Medicine..