By Amy Norton, Medical Tribune News Service
While physicians have known for years that daily doses of
aspirin help prevent stroke in people who are at-risk, new findings
show that low-dose aspirin is apparently more effective than higher
doses for people with clogged neck arteries.
In an international study of more than 2,800 patients with
severe blockages in the carotid arteries that supply blood to the
brain, researchers found that treatment with 81 mg and 325 mg of
aspirin bested higher doses in lowering patients' risk for stroke,
heart attack and death.
The patients also underwent carotid endarterectomy -- a procedure
used to ward off stroke by removing fatty deposits from the carotid
artery. Because it's been unclear how much aspirin is best for
patients recovering from the surgery, researchers led by D. Wayne
Taylor aimed to identify a dose range.
Taylor, a professor of clinical epidemiology at McMaster
University in Ontario, Canada, and colleagues reported their
findings in Saturday's issue of The Lancet.
The researchers divided the patients into four groups: two
low-dose aspirin groups, one taking 81 milligrams per day and the
other 325 milligrams; and two high-dose groups on either 650
milligrams or 1,300 milligrams of aspirin per day. All patients
began aspirin therapy three days before surgery and continued for
three months afterward.
At the end of the three months, Taylor's team found significant
differences between the low-dose and high-dose groups in rates of
stroke, heart attack and death.
Among low-dose patients, 3.2 percent had suffered a stroke,
compared with 6.9 percent of high-dose patients; heart-attack rates
were 0.9 percent and 3.3 percent, respectively; and death rates
were 1.6 percent and 2.2 percent, respectively. There were no
significant differences between the two low-dose groups or between
the high-dose groups, according to the report.
As for the side effects that can accompany aspirin use -- such as
gastrointestinal upset and bleeding -- there was no difference among
any of the doses. In all groups, between 23 percent and 27 percent
of patients experienced a gastric side effect, most often stomach
upset.
Since most strokes occur when blood flow to the brain is
impeded, therapy to reduce blood clotting, including aspirin use,
has become an important part of stroke prevention. An estimated 10
percent to 30 percent of the 500,000 strokes that occur in the
United States each year are a result of blockage in the carotid
artery.
After carotid endarterectomy to remove the blockage, clotting in
the artery and subsequent strokes remain a concern. This study,
Taylor's team reported, shows that lower doses of aspirin
effectively cuts this post-surgery risk. Still, the researchers
cautioned against ``over-generalizing'' the study results to all
patients at risk for stroke. Risk factors for stroke include high
blood pressure, the artery disease atherosclerosis, smoking and a
history of transient ischemic attacks, or ``mini-strokes.''
One expert, however, said physicians can now feel ``more
comfortable'' recommending low-dose aspirin for stroke prevention
in general.
Because the optimal dose has been unclear, many doctors
recommend one aspirin per day, while others favor up to four pills
a day, according to Dr. John Marler, associate director for
clinical trials at the National Institute of Neurological Disorders
and Stroke (NINDS) in Bethesda, Md.
The Taylor study, according to Marler, should be ``reassuring''
for doctors who choose the one-aspirin-a-day route. ``Low-dose
aspirin is at least as good [as high-dose], and is probably
better,'' he said.
In the broader scope, Marler added, ``this is one more example
of how amazing aspirin is.''
Because aspirin also reduces the risk for heart attack, Marler
advised anyone older than 50 to discuss daily aspirin use with his
or her doctor.
