Aspirin Cuts Risk of One Type of Stroke
Regular doses of aspirin or a common blood thinner can cut in half a person’s risk of stroke from an irregular heartbeat--a striking discovery announced Wednesday that U.S. health officials say could prevent 30,000 or more strokes a year in the United States.
The finding that aspirin or the blood thinner warfarin can safely prevent stroke in people with so-called atrial fibrillation suggests yet another use for aspirin, the medicine-cabinet mainstay shown recently to help prevent heart attacks in men over 50.
“This is a big breakthrough in stroke prevention,” said Dr. Merrill Kanter of the University of Texas, one of the researchers on the study. “With this type of information, we hopefully could go on and learn more about stroke prevention in other areas.”
The finding emerged from a large federally funded study of 1,244 men and women with atrial fibrillation. The condition affects more than 1 million Americans, placing them at five times the normal risk of a certain type of stroke.
The researchers interrupted the study 18 months early amid strong indications that one aspirin a day or regular doses of warfarin cut the chance of stroke and blood clots by 50% to 80%--while causing little significant rise in the risk of uncontrolled bleeding.
The study is now continuing in order to determine which drug is more effective and safer in specific types of patients. But the researchers said the findings are sufficiently solid to justify a change in the care of atrial fibrillation patients.
“The findings change the general recommendations for medical care,” said Dr. John McAnulty of Oregon Health Sciences University. Until now, he said, the benefit of blood thinners was unproven and some physicians feared they carried unwarranted risks.
“The bottom line is, if you have atrial fibrillation, you and your physician should seriously discuss whether you should be on one of these treatments or not,” said Dr. Michael D. Walker of the National Institute of Neurologic Disorders and Stroke.
Researchers urged patients to confer with their doctors before taking any drugs. As many as a quarter of all atrial fibrillation patients could be ineligible for the treatment because other conditions, such as peptic ulcers, leave them at excessive risk of bleeding.
Nevertheless, Walker’s institute, which funded the study, predicted that aspirin or warfarin therapy could prevent 100 to 150 strokes a day nationwide. The institute estimated the health care savings at more than $200 million a year.
Atrial fibrillation is a condition in which the upper chambers of the heart, or atria, beat irregularly and rapidly. Because not all the beats pass on to the lower chambers of the heart as they should, those lower chambers also beat irregularly, but at a slower rate.
Because blood is not pumped through the heart quickly and smoothly, it pools in the upper chambers and can result in the formation of clots. Those clots can enter the bloodstream and lodge in an artery in the brain, blocking blood flow and causing a so-called ischemic stroke.
About 75,000 strokes a year in the United States are associated with atrial fibrillation. Researchers estimate that perhaps half of all strokes result in significant neurological damage interfering with a person’s ability to function and even to think.
(A stroke can also be caused by clogging of a brain artery or rupture of a blood vessel in the brain. Researchers are currently studying whether aspirin can prevent strokes in people whose arteries have begun to clog.)
Warfarin, also known by its brand name, Coumadin, affects chemicals in the body that cause the blood to clot. Aspirin prevents platelets--small blood particles that play a central role in blood clotting--from joining to form a clot.
In the new study, published today in the New England Journal of Medicine, patients were assigned to one of two groups. The patients in one group received either warfarin, aspirin or a placebo; those in the other group received either aspirin or a placebo.
In the first group, those on a placebo had a stroke or clot rate of 8.3% per year. Those on warfarin or aspirin had a stroke or clot rate of 1.6%. In the second group, the rates were 6.3% among patients on a placebo and 3.2% among patients on aspirin.
Patients over age 75 experienced no benefit from aspirin, the researchers found.
“This came as a big surprise to us,” said Dr. Robert G. Hart of the University of Texas Health Science Center in San Antonio. “It was quite unexpected. . . . There are several theories, one of them being that maybe aspirin absorption may be different as you get older. We don’t know right now.”
In general, the researchers avoided giving warfarin to patients over age 75. Warfarin is believed to pose a slightly greater risk of uncontrolled bleeding than does aspirin.
Spokesmen for several aspirin companies said Wednesday that they had not seen the study and could not comment in detail on its implications.
Times staff writer Marlene Cimons in Washington contributed to this story.
