By Alicia Chang,AP Science Writer

People at risk of developing strokes caused by narrowed arteries in the brain should consider aspirin instead of a common anti-clotting drug, new research suggests.

Aspirin worked just as well as warfarin in stroke patients with narrowed brain arteries, according to a study of 569 people at more than 50 sites across North America. But those on warfarin, which is marketed as Coumadin, suffered a higher death rate and more major bleeding compared to those who took aspirin.

Results appear in Thursday’s New England Journal of Medicine.

The study was done in patients who had suffered a stroke or mini-stroke as a result of a condition called symptomatic intracranial arterial stenosis. It is caused by the buildup of fatty deposits in the arteries’ inner walls, restricting blood flow. It’s unknown just how many people have the disorder, but it causes about 10 percent of the 900,000 strokes and mini-strokes that occur in the United States each year.

People with the condition currently take aspirin or warfarin to reduce stroke risk. Both work by thinning the blood, warding off clots that can block blood vessels.

Dr. Marc Chimowitz, a neurologist at Emory University and lead author of the study, said people with the disorder should not automatically stop taking warfarin or start an aspirin regimen without first consulting their doctors.

He also noted that previous studies have shown the drug is useful in preventing strokes in people with other conditions like irregular heartbeat and clots in the legs and lungs.

In the latest study, patients randomly took either warfarin or high-dose aspirin. The aspirin group was given a daily dose of 1,300 milligrams, a higher amount than is recommended for heart disease and general stroke prevention. Researchers used the higher dose based on previous studies on its effectiveness. It was unclear whether another aspirin dose would lead to better results, Chimowitz said.

During follow-up, about one in five patients died from circulatory problems, had a second stroke or suffered brain hemorrhaging regardless of which drug they took. But the warfarin patients developed complications at a higher rate. Nearly 10 percent of them died compared to 4 percent who took aspirin. Those who took warfarin also had higher risks of major bleeding and suffering a heart attack or sudden death.

Dr. Jay Mohr, a neurologist who had no role in the study, said the results may force doctors to rethink the effectiveness of warfarin in stroke prevention.

“This will further influence doctors away from making a decision favoring warfarin as the strongest therapy,” said Mohr of the Columbia University Medical Center in New York City.

The $15 million study, funded by the National Institutes of Health, was to last five years, but enrollment was halted midway after concerns were raised about the side effects associated with the group taking warfarin.