HOW PASSIVE SMOKING CAUSES HEART DISEASE
by Sean Henahan, Access Excellence
SAN FRANCISCO- Recent studies provide a better
understanding of the mechanisms by which second hand tobacco
smoke contributes to the development of heart disease, report
researchers from UC San Francisco.
Two noted cardiology researchers, Dr. Stanton Glantz and Dr.
William Parmley, have done a considerable amount of research on
the effects of secondhand tobacco smoke on the heart. The two
collaborated on a research project combining their own data with
that from other researchers around the world, in an effort to
consolidate what is known about the pathogenic mechanisms of
The current data demonstrate that the ill effects of
secondhand smoke result from many components of tobacco smoke.
These include carbon monoxide, nicotine, polycyclic aromatic
hydrocarbons and others.
The carbon monoxide produced by passive smoking competes
with oxygen for binding sites on red blood cells. This reduces
the blood's ability to deliver oxygen to the heart and
compromises the heart muscle's ability to use oxygen to create
adenosine triphosphate. The carbon monoxide also increases the
amount of lactate in venous blood.
As a result of these effects, people exposed to second hand
smoke show a reduced exercise capability. For example, studies
show that people with existing heart disease cannot exercise as
hard or as long when exposed to secondhand smoke. These people
are also more likely to develop arrhythmias (irregular heart
beats) when exposed to secondhand smoke. Related studies have
shown that people with no signs of heart disease take as long as
those with heart disease to return to their resting heart rate
following exercise when exposed to secondhand smoke.
Several studies have shown that children of smoking parents
have increased levels of 2,3-diphosphoglycerate. This enzyme
increases the disassociation of oxygen from hemoglobin in red
blood cells in an attempt to counterbalance chronic oxygen
Second hand smoke, also called sidestream smoke or
environmental tobacco smoke, also increases platelet activity,
accelerates atherosclerotic lesions, and increases tissue damage
following ischemia (insufficient oxygen delivery to the heart or
brain) or myocardial infarction (heart attack). Increases in
platelet activity are associated with formation of blood clots
and atherosclerosis (hardening of the arteries), both of which
are factors predisposing for a heart attack.
There is now a considerable amount of data indicating that
second hand smoke has different effects on smokers and
non-smokers, the researchers note. The hearts of chronic smokers
make certain adaptations to compensate for the negative effects
of smoking, whereas nonsmokers do not show this 'advantage'.
"The practice-- often advocated by the tobacco industry and
its scientific consultants when considering second hand smoke--
of thinking about cigarette equivalents of simple dose-based
extrapolations from smokers to non-smokers will lead to gross
underestimations of the risks of passive smoking to the
cardiovascular system... Leaving aside the philosophical
considerations of whether anyone ought to be required to breathe
even one cigarette per day under any circumstances, the
environmental tobacco smoke experienceed by many people in their
daily lives is enough to produce substantial adverse effects on
the cardiovascular system," note Parmley and Glantz.
The researchers conclude that second hand smoke is the third
leading cause of preventable death, after active smoking and
alcohol. They estimate that passive smoking causes as many as
60,000 fatal heart attacks per year and three times as many
non-fatal heart attacks.
Passive smoking should be considered on a par with public
health problems such as AIDS and illegal drug use, with major
efforts expended to protect workers, children and the general
public, they note, adding that the simplest and least expensive
way to accomplish this is to mandate smoke-free workplaces,
schools and public places.
For complete details on this study, see Glantz et al.,
JAMA, , 4/5/95, V.273, No.13, pp.1047-1053.
Transmitted: 95-04-08 11:57:50 EDT
Related information at other Web sites:
Smoking, Tobacco and Cancer at Oncolink
The Franklin Institute's Virtual Heart