Study:
Pollution elevates risks for exercising heart patients
By LINDA A. JOHNSON
Associated Press Writer
TRENTON, New Jersey (AP) - People with heart disease may want
to avoid heavy traffic when exercising or simply take their
workout indoors to avoid breathing polluted air.
Exercising in areas with high levels of diesel
exhaust and microscopic soot particles is especially risky
for people with heart disease, according to the first study
in which heart patients were directly exposed to pollution.
European researchers found that brief exposure
to diluted diesel exhaust during exercise reduced a key anticlotting
substance in the blood and worsened exercise-induced ischemia,
or insufficient flow of blood and oxygen to the heart _ changes
that can trigger a heart attack and even death.
"We now have evidence that being exposed
to diesel fuel during exercise will cause cardiac ischemia
and that if you have heart disease, it can only make things
worse," said Dr. Abraham Sanders, a lung specialist at
New York-Presbyterian Hospital who was not involved in the
study.
The results have big implications: About 16
million Americans have heart disease, according to the American
Heart Association. In addition, people with asthma, bronchitis
and chronic obstructive pulmonary disease also should use
caution and avoid polluted air when exercising, Sanders recommended.
But heart and respiratory patients should keep exercising
regularly because it is so beneficial to overall health, doctors
stress.
Numerous studies have shown a link between
short-term and long-term exposure to air pollution and higher
rates of hospitalizations and deaths due to poor blood supply
to the heart, abnormal heart rhythms, gradual heart failure
and stroke.
This study adds to that knowledge about how
air pollution harms people and aims to show what pollution
is doing in the body, information that might eventually give
clues for preventing such problems, said Dr. Howard M. Kipen,
director of clinical research at Rutgers University's Environmental
and Occupational Health Sciences Institute.
"It's quite amazing, what they found,"
but not a surprise, he said. Still, "most doctors aren't
aware that little bits of pollution can cause heart attacks."
The European study was reported in Thursday's
New England Journal of Medicine.
Researchers in Sweden and the United Kingdom
tested 20 men aged about 60 who had survived a heart attack
at least six months earlier, had blockages cleared and propped
open with a stent, and were getting treatment to prevent a
second heart attack. The researchers noted they only tested
men with stable heart disease and good tolerance for exercise,
and monitored each closely to ensure none suffered any health
problems.
On two separate occasions, each man was put
in an enclosed chamber for an hour and exposed to either diluted
diesel exhaust or clean, filtered air. They rode an exercise
bike for two 15-minute periods and rested in between. The
men had electrodes attached to their bodies to monitor the
heart's electrical activity.
While exercising and exposed to diesel exhaust,
the men experienced drops in the heart's electrical activity
two to six times greater than when they were breathing filtered
air. Those reductions indicated the heart muscles were not
getting enough blood.
While diesel exhaust contains many harmful
chemicals, the researchers said they believe that particulates
in the exhaust are the main harm to the heart patients.
A 2000 study in six U.S. cities found the
strongest association between risk of death in heart patients
and air pollution exposure was for microscopic air particulates,
such as those in diesel exhaust.
The European researchers noted particulate
concentrations can regularly hit 300 micrograms per cubic
meter _ the level to which the study participants were exposed
_ in heavy traffic, workplaces such as factories and refineries
and in the world's largest cities. Levels of some of the pollutants
in the diesel exhaust were far above the limits recommended
by the World Health Organization, they noted.
This study only included men, but Sanders
said he thinks the findings probably apply to women. A recent
report from the federal Women's Health Initiative found exercise
in polluted environments causes a temporary reduction in blood
flow to the heart muscle.
In an editorial, Dr. Murray A. Mittleman of
Beth Israel Deaconess Medical Center in Boston wrote, "these
findings may represent the tip of an iceberg" on how
spikes in air pollution levels affect cardiovascular risk.
___
On the Net:
New England Journal of Medicine: http://www.nejm.org
American Heart Association: http://www.americanheart.org/presenter.jhtml?identifier4419
