FRIDAY, Aug. 10, 2007 (HealthDay News) -- The largest study ever of its kind finds the clot-preventing drug warfarin to be more effective than aspirin in preventing strokes in older people with the abnormal heartbeat called atrial fibrillation.
The incidence of dangerous hemorrhages connected to the use of these anticlotting agents was also much lower than had been feared, British researchers report.
"My interpretation of the finding is warfarin ought to be the treatment of choice for such people over the age of 75," said lead researcher Dr. Jonathan Mant, a reader in stroke epidemiology at the University of Birmingham.
His team presented its findings in the Aug. 11 issue of the journal The Lancet.
Stroke is a constant threat for people with atrial fibrillation, in which the upper chambers of the heart quiver rather than regularly contract. This can disrupt the heart's pumping ability and send a clot from the heart to the brain, potentially causing stroke.
Warfarin, also known as Coumadin, has long been prescribed to prevent such strokes and has been more or less standard for most people with atrial fibrillation. However, its use for people over 75 has been limited due to fears of excess bleeding.
However, in the current study, Mant said, "we found that the risk of bleeding on warfarin was the same as on aspirin."
The study involved 973 people with atrial fibrillation, averaging 81 years of age. The number of participants may not seem large, but it is greater than the total of all the previous studies that have looked at the use of warfarin to prevent stroke in those 75 and older, Mant noted. Earlier trials tended to concentrate on non-elderly people, he said.
However, warfarin more than halved users' risk of stroke compared to aspirin. There were just 21 strokes in the warfarin group and 44 in the aspirin group during a follow-up period that averaged 2.7 years, the researchers reported.
Overall, there were two brain hemorrhages in the 488 participants who received warfarin, and one in those taking aspirin.
"This is a landmark study because of the large number of patients," said Dr. David A. Garcia, associate professor of internal medicine at the University of New Mexico, who wrote an accompanying editorial. "It certainly establishes that warfarin is the most effective way to prevent stroke in people with atrial fibrillation in that age group," he said.
Still, warfarin does carry a higher risk of excess bleeding, at least for some people, Garcia noted. "That subgroup is probably smaller than we once thought," he said. "What we need in the future is a way to identify those patients at high risk for bleeding, whether they are elderly or not, and at the moment, there still is work to be done to identify the patients at high risk prospectively."
Whenever he treats older people who have atrial fibrillation, "my own personal practice is to try very hard to get them on warfarin, because I know the benefit is extremely large for most patients, especially for those in this age group," Garcia said.
Use of warfarin often requires fairly frequent blood tests to monitor the International Normalized Ratio (INR), a measure of the ability of the blood to clot, Garcia said. British rules state that once the INR is well-controlled, blood tests can be done 12 weeks apart, Mant said.
There's more on preventing stroke at the American Stroke Association.