Aspirin in Heart Attack Prevention: How Much, How Long?
DURHAM, NC – A low dose of aspirin appears to be just as
effective as a higher dose in preventing a heart attack, stroke
or death among patients with stable cardiovascular disease, say
researchers at Duke University Medical Center.
Scientists also found that taking aspirin as a prevention
strategy doubled patients' risk of serious bleeding. Still,
they say that for most of the patients, the protective benefits
of taking aspirin daily far outweigh risk of any side
"Aspirin is one of the most commonly prescribed drugs in the
world and a mainstay in the treatment of heart attack," says
Dr. Jeffrey Berger, a cardiologist at the Duke Clinical
Research Institute, "but there is still considerable debate
over the optimal dose people should be taking on a regular
basis to prevent further problems."
The findings appear in the January issue of the American
Journal of Medicine.
Berger and his colleagues sifted through 40 years' worth of
clinical trials and found only six where researchers could
extract data comparing a low dose of aspirin (50 to 325
milligrams) against a placebo in the treatment of patients with
previous heart attack, angina or stroke.
In reviewing data from nearly 10,000 patients enrolled in
these trials, researchers discovered that those who took
aspirin daily had a 25 per cent reduction in the risk of
stroke, a 26 percent reduction in risk of a second heart attack
and a 13 percent lower risk of death, when compared with people
who took a placebo. Overall, in considering all types of
cardiovascular events, patients who took aspirin were 21
percent less likely to encounter potentially fatal problems
than those who did not take it.
When the researchers looked more closely at the benefits
gained from varying doses, they found no difference between
those who were taking only 50 milligrams per day and those who
were taking 325 milligrams per day.
They did note, however, that patients taking aspirin were
twice as likely to develop serious bleeding as those who did
not take it. "One in every 111 people who took low-dose aspirin
on a regular basis suffered significant bleeding, so aspirin
should be taken with caution," says Berger.
Although many doctors recognize that a lower dose of 81
milligrams of aspirin is just as effective – as well as safer –
than a higher dose for the prevention of heart disease, Berger
says most doctors are still prescribing 325 milligrams of
aspirin at the first sign of a heart attack. "It's just not
necessary; that's twice the amount patients really need," he
Aspirin helps protect a person from heart attacks because it
can break up platelets in the blood that tend to clump together
in clots that can block blood vessels and lead to chest pain or
heart attack. But aspirin therapy is a two-edged sword: It's
that same clot-busting ability that can lead to excess bleeding
in some people – bleeding serious enough to warrant
"This study tells us several things," says Berger. "First,
even though aspirin is relatively cheap and easily obtained as
an over-the-counter medication, we need to remember that it is
a very powerful drug, even in small doses."
At the same time, Berger says the study may give some
clinicians renewed appreciation for a lowly, often overlooked
aspirin tablet. "When you put aspirin up against much newer
medications like the cholesterol-lowering statins or blood
pressure-reducing ACE-inhibitors – which can be very expensive
– you see a similar pattern of benefit," he says.
To illustrate, Berger says physicians would need to treat
only 71 people with low dose aspirin to prevent a single death,
but they would have to treat 83 patients with a statin or 91
patients with an ACE-inhibitor to achieve the same result.
"In these days, when everyone's budget is tight, it's good
to know that good prevention strategies do not have to cost a
fortune," Berger says.
Berger's work is funded in part from a grant from the
American Heart Association.
Drs. Richard Becker from the Duke Clinical Research
Institute and David Brown, from the Stony Brook University
School of Medicine are co-authors of the study.