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Secondhand
Smoke
May
Impair Nonsmokers' Blood Flow
Excerpt
by Amy Norton
NEW YORK (Reuters
Health) - Even a brief bout with secondhand smoke may be enough
to temporarily slow down nonsmokers' blood circulation, new study
results suggest. The short-lived slowdown may help explain how,
over time, exposure to cigarette smoke can raise nonsmokers' heart
disease risk, according to investigators.
In a study
examining the impact of environmental cigarette smoke on heart
blood vessels, Japanese researchers found that 30 minutes of exposure
to secondhand smoke reduced nonsmokers' coronary flow velocity
reserve (CFVR)--a measure of the speed of blood flow.
CFVR readings
provide a way to non-invasively gauge how well the cells that
line blood vessels are working. These cells, called endothelial
cells, help vessels dilate in response to blood flow and help
prevent blockages from forming. Dysfunction in endothelial cells
contributes to the narrowing and hardening of heart arteries.
According
to Dr. Ryo Otsuka and colleagues at Osaka City University Medical
School, their findings provide ``direct evidence that passive
smoking may cause endothelial dysfunction of the coronary circulation
in nonsmokers.'' They report the results in the July 25th issue
of The Journal of the American Medical Association.
In an accompanying
editorial, doctors from the University of California, San Francisco
note that ``the findings...are important not only because they
illustrate the importance of preventing nonsmokers from any exposure
to secondhand smoke, but also because they help to explain the
relatively large risk of death and other cardiac events associated
with passive smoking.''
This study
``adds substantially'' to the belief that exposure to secondhand
smoke can ``immediately compromise the cardiovascular system,''
according to Drs. Stanton A. Glantz and William W. Parmley.
``If you sit
in a smoky bar for 30 minutes, your endothelial function is temporarily
compromised to the level of a pack-a-day smoker,'' Glantz said
in an interview with Reuters Health.
According
to Glantz, the findings counter tobacco industry claims that a
nonsmoker would have to sit in a smoky environment for ``hours
and hours'' to sustain the immediate damaging effects of smoking
one cigarette.
This study,
he said, shows the short-term effects of secondhand smoke are
``way out of proportion to the dose.''
In their study,
the Japanese researchers used a type of ultrasound to measure
CFVR in 30 healthy men, half of whom were smokers. They took measurements
before and after exposing the men to secondhand tobacco smoke.
Before exposure,
nonsmokers' CFVR was substantially higher than that of smokers.
But after exposure, their measurements dropped to match those
of the smokers--whose CFVR was largely unaffected by the secondhand
smoke.
``The present
study,'' Otsuka's team writes, ``is the first to demonstrate that
passive smoking may have a stronger impact on CFVR in nonsmokers
than in active smokers.''
Passive smoking
did not have any effect on nonsmokers' heart rate or blood pressure.
However, the researchers conclude that the changes they saw in
participants' blood vessel function may be one reason why passive
smoking has been linked to heart disease in nonsmokers.
According
to Glantz and Parmley, the findings also bolster the belief that
``everyone should be protected from even short-term exposure to
the toxins in secondhand smoke.'' This, they argue, includes designating
more workplaces, restaurants and bars ``smoke-free.''
Glantz said
it is unclear how much exposure to secondhand smoke is necessary
to raise a nonsmokers' heart disease risk. But he noted that people
who live with smokers have been found to have a 30% increase in
their risk.
SOURCE:
The Journal of the American Medical Association 2001;286:436-441,
Reference
Source 89
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