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Cause of Most Heart Attacks Found
Researchers Say They May Know What Causes 90%
of Heart Attacks
By
Peggy Peck
Reviewed By Michael Smith, MD
on Monday, August 30, 2004
WebMD Medical News
Aug.
30, 2004 (Munich, Germany) -- Heart researchers
say nine risk factors -- ones that you can do
something about -- account for 90% of all heart
attacks.
Previously,
researchers thought that only about half of heart
attacks were explained by risk factors such as
smoking or cholesterol. But now they say that
the cause of almost all heart attacks can be pinpointed
to one or more of the following:
Smoking
Abnormal cholesterol
Diabetes
High blood pressure
Stress
Abdominal obesity
Sedentary lifestyle
Eating too few fruits and vegetables
Abstaining from alcohol
These
risk factors are equal-opportunity killers --
black or white, Asian or American, young or old,
man or woman -- all can fall victim by these same
risks. Diet, exercise, and moderate consumption
of alcohol can decrease risk of heart disease,
but cannot reverse the potential danger posed
by risks such as high cholesterol or smoking,
says Salim Yusuf, MD, who led the study.
The
study included nearly 30,000 people -- half were
first heart attack survivors and half were healthy
volunteers of similar age, race, and gender to
the heart attack patients. Since the study was
conducted in 52 countries located on every populated
continent, Yusuf tells WebMD that it is now possible
to say that "the same risk factor that causes
a heart attack in a white European will cause
a heart attack in an Asian."
Bigger
Waist, Bigger Risk
Rather
than relying on body mass index (BMI), the researchers
took waist measurements. A waist circumference
of more than 80 centimeters (32 inches) in women
and more than 85 centimeters (34 inches) in men
increased risk. Yusuf says measuring the waist
is a better predictor of heart attack risk because
"it is a measure of abdominal fat, which
is the type of fat that is most closely associated
with heart attacks."
Yusuf
presented the study results at the European Society
of Cardiology meeting. He says that cholesterol
size also plays a role in determining risks. Smaller,
denser cholesterol molecules increase the risk
of heart disease; these can more easily invade
the artery wall causing inflammation and atherosclerosis
plaque. The higher the amounts of smaller and
denser particles, the higher the risks relative
to larger cholesterol particles.
He
says that this factor alone may increase the risk
of heart attacks by as much as 54%. Yet when a
smoker has a bad lipid ratio (smaller to larger
particles) "that combination accounts for
two-thirds of heart disease."
In
the study researchers measured particles which
carry cholesterol in the blood called apoproteins.
The ratio of apoliprotein B (which carries "bad"
LDL cholesterol) and apoliprotein A-1 (which carries
"good" HDL cholesterol) is a much simpler
test, Yusuf says. "I call it the ratio of
nasty versus good molecules."
People
at the highest risk for the ApoB/Apo A-1 ratio
increased their risk of heart attack by 54%, he
said.
Second
on the nine-item list is smoking which was associated
with a 36% increased risk of heart attack. And
Yusuf warns that risk increases with the first
cigarette: smoking one to five cigarettes a day
increases heart attack risk by 40% compared with
nonsmokers. Smoking 20 cigarettes a day (one pack)
is associated with a fourfold increased risk of
heart attack and smoking two or more packs a day
"is associated with a ninefold increased
risk," he says.
Moreover,
while a daily low-dose aspirin can protect the
heart, "smoking three cigarettes can wipe
out the protective effect of aspirin and wipe
out two-thirds of the protective effect of [cholesterol-lowering
drugs]," he says.
Calling
the study the "most important work of my
life," Yusuf says that the power of some
risk factors was surprising. For example, he says
that stress, which he previously considered a
"soft" risk factor, actually doubled
the risk of heart attack. The study indicates
that stress is most dangerous when it is described
as "permanent" and when stress is constant
whether at home or at work. Moreover, people who
say they have little control on the job or in
the home are more likely to suffer stress-related
heart disease.
Rounding
out the list of risk factors were diabetes, high
blood pressure, sedentary life style, and a diet
that doesn't include generous servings of fruits
and vegetables. On the positive side, a good diet,
regular exercise, and moderate alcohol intake
did reduce the risk of heart disease -- again
the reduction was the same regardless of race
or ethnicity.
Richard
Horton, MD, editor of The Lancet, says that the
study demonstrates the potential for real health
benefits that can be achieved without pills or
surgery. Horton says the results indicate the
need for "political action. I think it is
really time to consider political moves to control
the food industry." Among the possible options
would be special taxes on foods known to contribute
to obesity or limits on where such foods can be
sold. Horton was not involved in the study.
Yusuf
agrees that a concerted, international effort
could greatly reduce what he calls a pandemic
of heart disease. "We need to build healthier
environments," he says. "Shopping, work,
and residence should be concentrated in the same
area so that people can walk to a store or walk
to work or school."
The
study received funding from 39 institutions including
the Canadian Institutes of Health Research and
the Heart and Stroke Foundation of Ontario as
well as a number of pharmaceutical companies.
--------------------------------------------------------------------------------
SOURCES:
European Society of Cardiology meeting, Munich,
Germany, Aug. 29-Sept. 1, 2004 Hotline I: Prevention
and Medical Treatment. Session 104 presented Aug.
29, 2004 "INTER-HEART: a study of risk factors
for first myocardial infarction in 52 countries
and over 27,000 subjects." Salim Yusuf, MD,
professor of medicine, McMaster University, Hamilton,
Ontario, Canada. Richard Horton, MD, The Lancet,
London.
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