SHOULD YOU TAKE A DAILY ASPIRIN
A series of recent
studies has made people ask whether acetylsalicylic acid, better
known as Aspirin, really is beneficial for your heart. As most
people know, Aspirin is fixture in the field of cardiology and
is routinely prescribed to people with heart disease. However,
it was a relatively late arrival to the field. The ISIS-2 study,
which showed that giving patients Aspirin after a heart attack
improved survival, was only published in 1988. Nevertheless,
subsequent studies, and a large meta-analysis by the Antithrombotic
Trialists Collaboration, showed that Aspirin prevented recurrent
events and established it as the standard of care.
Although
the use of Aspirin after a heart attack (what we term secondary
prevention) has a very clear benefit, giving Aspirin to patients
before they have a heart attack (primary prevention) is not
as clear cut. Even back in 1988, some studies were equivocal
about whether Aspirin was beneficial for patients without heart
disease. Subsequent studies have been variable, although some
did show a reduction in non-fatal events though no reduction
in mortality. A meta-analysis found that the reduction in serious
vascular events was minimal (less than 0.1 per cent) and largely
offset by the increased risk of bleeding.
Thus,
the current set of studies in the New England Journal of Medicine
should not be entirely surprising. The first study looked at
patients with diabetes but no history of heart disease. It found
that while Aspirin decreased the incidence of major vascular
events by about 1 per cent, this benefit was counterbalanced
by a 1-per-cent increase in the risk of bleeding.
The
other two studies looked patients who were age 70 and above.
These were significant studies because older patients are often
underrepresented in clinical trials. In the first of the two
studies, daily Aspirin use had no effect on preventing heart
attacks and increased the risk of bleeding, although the increase
was fairly minor at two extra bleeds per 1,000 people.
The
second of the two studies generated more headlines. Using the
same patient population of patients older than 70 years, it
found that daily Aspirin use increased the risk of dying by
about 1 per 1,000 people. These excess deaths were not actually
cardiac deaths but were, strangely enough, due to an excess
in cancer-related deaths, which the authors of the paper said
were “unexpected and should be interpreted with caution.”
The
notion that Aspirin can precipitate cancer deaths is somewhat
hard to believe. There is already some pretty compelling evidence
that Aspirin can reduce the risk of colorectal cancer. Also
just a few weeks after the papers were published, two studies
came out suggesting Aspirin might decrease the risk of liver
cancer and ovarian cancer. Although these observational studies
are less compelling than the evidence for colon cancer, it seems
pretty clear that, overall, Aspirin, if anything, decreases
cancer risk rather than increases it.
There
is a common and oft repeated saying that everyone over 50 should
take a baby Aspirin once a day. It is not entirely clear, to
me at least, where this idea originated, but many people hold
to it. For patients who have a history of heart disease or stroke,
the benefit of Aspirin is fairly clear. However, for patients
who have never head a heart attack of stroke, the benefit of
daily Aspirin is more modest, possibly not clinically significant,
and potentially offset by the risk of bleeding. Whether you
should take a daily Aspirin is dependent on your cardiovascular
risk, which depends on risk factors like age, diabetes, blood
pressure, cholesterol and smoking status, and must be weighed
against the risk of bleeding.
As
with most things in medicine, deciding whether you would benefit
from a daily Aspirin is not a simple yes or no question. It
is much more complicated.
