The long
reach of cigarette smoke
(This article was first printed in the September
2004 issue of the Harvard Heart Letter.
For more information or to order, please go
to www.health.harvard.edu/heart.)
New research extends the case against secondhand
smoke by linking it to heart disease.
Smoking, first fingered as a prime cause of
lung cancer, also contributes to heart disease.
Compared with nonsmokers, smokers have double
the chances of having a heart attack or stroke,
developing other forms of heart disease, or dying
from heart disease. Several 2004 studies indicate
that smokers also harm the hearts of nonsmokers
around them.
The health effects of secondhand smoke are at
the center of an acrimonious and politically
charged debate. Studies linking secondhand smoke
to disease are routinely used to support local
or statewide bans on smoking in public places.
Inconclusive or negative studies are cited to
challenge such laws. The studies aren’t
the final nails in the coffin for secondhand
smoke. But they do nudge the debate forward.
Smoking ban and heart attacks
In the city of Helena, Montana, a law that banned
smoking in restaurants, bars, offices, and other
public venues was in place for six months before
a judge overturned it. During the ban, the number
of people seen for heart attacks at the only
cardiac care hospital for miles was only half
of what it had been before the law was enacted
and after it had been struck down.
Writing in the April 24, 2004British Medical
Journal, the local cardiologists who carried
out the widely publicized study acknowledged
its limitations. These include Helena’s
small size and lack of knowledge about heart
attack victims’ exposure to secondhand
smoke. That said, they conclude that the establishment
of smoke-free public places could have a quick
and beneficial effect on heart disease.
Living with a smoker
New Zealand researchers tried to gauge the
effects of secondhand smoke a different way.
Using data from a nationwide census in 1981 and
another in 1996, they compared death rates among
two groups of people who said they had never
smoked — those who lived with smokers and
those who lived with nonsmokers. Death rates
were 15% higher among those who breathed secondhand
smoke at home. This report, which also appeared
in the April 24, 2004 British Medical Journal,
may underestimate the impact of secondhand smoke
because it didn’t take into account nonsmokers’ exposure
at work or elsewhere outside the home.
Evidence in the blood
Blood levels of cotinine (KOE-tin-een), a substance
formed when the body breaks down nicotine, are
one way to measure exposure to smoke. A team
of British researchers looked at cotinine levels
in more than 2,000 men who said they didn’t
smoke to gauge the impact of secondhand smoke.
Cotinine levels were closely linked with exposure
to secondhand smoke and to heart disease. After
20 years of follow-up, 18% of the men with the
highest cotinine levels had developed heart disease — the
same percentage as light smokers — compared
to 10% of those with the lowest levels. The British
Medical Journal published this work online
on June 30, 2004.
Impact of secondhand smoke
Cigarette smoke contains more than 4,000 substances.
Nicotine, one of the best known, is the prime
addictive element. A host of others either generate
free radicals or get the body to do so. These
highly reactive chemicals are thought to set
off early steps of atherosclerosis. Cigarette
smoke also revs up inflammation, another process
at the root of heart disease.
One of the mysteries of secondhand smoke is
how it can cause nearly the same level of damage
as smoking. A leading idea is that even a brief
exposure to secondhand smoke can suddenly limit
the flexibility of arteries.
Several studies support this line of thinking.
One of the most telling looked at how the heart’s
arteries respond to stress before and after brief
exposures to secondhand smoke. Smokers weren’t
affected — blood flow through their coronary
arteries didn’t change after sitting for
half an hour in a smoke-filled room. In nonsmokers,
though, breathing cigarette smoke restricted
the ability of coronary arteries to widen and
carry more blood when stressed.
Secondhand smoke also makes blood more likely
to clot. The combination of less flexible arteries
and an increased tendency to form blood clots
creates a double whammy that could trigger a
heart attack, especially in nonsmokers who already
have heart disease.
The Centers for Disease Control and Prevention
(CDC) estimates that secondhand smoke is responsible
for 35,000 deaths a year. It’s a special
risk for people who work in smoke-filled rooms,
like waitresses and bartenders. In fact, the
CDC now urges people with heart disease or at
high risk for it to stay away from indoor settings
where smoking is allowed.
This work on secondhand smoke won’t end
the debate on who can smoke where. But it does
add to the evidence that tobacco smoke affects
more than just smokers.
If you smoke, you need to know that your habit
directly affects the health of others. If you
don’t smoke, don’t hesitate to ask
a smoker to “take it outside,” especially
if you have heart disease. The evidence is in
your corner that secondhand smoke is more than
just a nuisance — it’s also bad for
you.
(This article was first printed in the September
2004 issue of the Harvard Heart Letter.
For more information or to order, please go
to www.health.harvard.edu/heart.)
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