What's So Passive About Passive Smoking?
March 30, 1998
What's So Passive About Passive Smoking?
ABSTRACTS & COMMENTARY
Synopsis: Recent evidence shows that never smokers exposed to ETS have an increased risk not only of lung cancer but also of cardiovascular disease.
Sources: Howard G, et al. JAMA 1998;279:119-124; Werner R, Pearson TA. JAMA 1998;279:157-158.
Werner and pearson point out that cigarette smoking represents the single most important preventable cause of death in the United States. "The morbidity and mortality secondary to tobacco smoke have been dismissed by the tobacco industry because smokers have a choice in whether they smoke and are generally aware of the risks associated with smoking. However, this argument does not extend to the millions of people who are exposed to tobacco smoke not as active smokers but by inhalation of environmental tobacco smoke (ETS)."
There are 480,000 smoking-related deaths estimated to occur each year in the United States. Around 53,000 of these are attributed to ETS.1 Werner and Pearson point out that recent evidence shows that never smokers exposed to ETS have an increased risk not only of lung cancer but also of cardiovascular disease.2
In the same issue of JAMA, Howard and colleagues compared the effects of active smoking, ETS, and never smokers on the progression of arteriosclerosis by using carotid artery internal-medial thickness (IMT) as an end point.
There was a total of 10,914 participants from the Atherosclerosis Risk in Communities study. The main outcome measure was a change from the baseline to the three-year follow-up as indexed by changes in IMT of the carotid artery assessed by ultrasound.
Exposure to cigarette smoke was associated with progression of atherosclerosis. After adjustments for demographics, cardiovascular risk factors, and lifestyle variables, current smoking was associated with a 50% increase in progression of atherosclerosis. Past smoking was associated with a 25% increase. Exposure to ETS was associated with a 20% increase relative to those not exposed. The effect of smoking was greater for subjects with diabetes and hypertension. More pack years of smoking, but not current vs. past smoking, was associated with progression of atherosclerosis. This suggests that some of the adverse effects of smoking may be cumulative and irreversible.
COMMENT BY RALPH R. HALL, MD
Werner and Pearson ask if internal-medial thickening is a valid marker for advancing arteriosclerotic disease. They cite specific references, which indeed confirm that this is an objective measure of advancing arteriosclerosis. It is difficult to ignore the magnitude of the changes found in this study.
Past studies have not examined or documented the exposure to passive smoking to the extent that these researchers have. It appears that this should be included in the histories we obtain from our patients. Simply asking the question will be educational for the patient and may explain, as Werner and Pearson point out, why some patients with no other apparent risk factors develop arteriosclerotic heart disease at an early age.
It has been clearly demonstrated that endothelial dysfunction and increased platelet aggravation occur as a result of exposure to environmental smoke. This initiates smooth muscle proliferation, leading to arteriosclerotic plaque formation.
The public health implications of this research are immense. What's so passive about passive smoke?
References
1. Glantz SA, Parmlig WW. Circulation 1991;83:1-12.
2. U.S. Environmental Protection Agency. Washington, DC. 1992 Publication, 600/6-90/006F.
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