By DAVID WILLIAMSON
UNC-CH News Services
(Embargoed) CHAPEL HILL -- Both active and passive smoking speed up the process by which arteries become clogged and increase the risk of strokes and heart attacks, according to a major new study.
The arterial disease process, which laymen call hardening of the arteries and scientists call atherosclerosis, develops even faster among smokers suffering from high blood pressure or diabetes, the research shows.
The damage -- sometimes likened to rust building up in iron pipes and restricting water flow -- may be irreversible.
A report on the study, based at the University of North Carolina at Chapel Hill School of Public Health, appears in the Jan. 14 issue of the Journal of the American Medical Association. The investigation was conducted on almost 11,000 volunteers in North Carolina, Maryland, Minnesota and Mississippi.
"These data represent the first report, to our knowledge, from a large population-based study of the impact of active smoking and exposure to environmental tobacco smoke on the progression of atherosclerosis," wrote lead author Dr. George Howard, professor of biostatistics at Wake Forest University School of Medicine.
"Active smoking was found to play a major role in the progression of atherosclerosis, as did the duration of smoking measured by pack-years of exposure," Howard wrote. "The impact of exposure to environmental tobacco smoke on atherosclerosis...was also surprisingly large, increasing the progression rate by 11 percent above those not so exposed."
The findings suggest that the effects of smoking on atherosclerosis may be both cumulative and irreversible, he said.
The study involved using ultrasound devices to measure fatty deposit buildup on the inner walls of the carotid arteries of 10,914 volunteers enrolled in the Chapel Hill-based project. Researchers compared measurements when volunteers began in the study and then again three years later.
They found that cigarette smokers suffered a 50 percent greater accumulation of plaque than people who had never smoked. Former smokers showed a 25 percent higher level. Perhaps more disturbing was that compared to people never exposed to secondhand smoke, nonsmokers exposed regularly showed a 20 percent increase in disease progression. Diabetic and hypertensive people face two to three times the risk of accelerated atherosclerosis as otherwise healthy people.
Quitting smoking would stop hastening atherosclerosis, Howard said. Quitting probably will not reverse damage already done, however.
"It is shocking to me that nonsmokers exposed to secondhand smoke still face about a third of the risk of smokers," he said. "Quitting not only would help smokers, but also help protect their children."
In an editorial, Rachel M. Werner and Thomas A. Pearson of the University of Rochester write cigarette smoking represents the single most important preventable cause of death in the United States. They add that not much about passive smoking is passive.
"However, what is passive is our lack of recognition of the importance of passive smoke as a cardiovascular disease risk factor, our oversight in not asking patients about this exposure and our lack of advocacy for clean air as a way to help prevent chronic disease," they write.
"Avoiding environmental tobacco smoke should be given the same priority that is given to smoking cessation as a way to prevent disease, especially among persons with existing cardiovascular disease, diabetes, hypertension and other cardiovascular risk factors."
The National Heart, Lung and Blood Institute supports the continuing study.
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Note: Howard can be reached at (336) 716-2865. Dr. Sidney Smith, chief of cardiology at UNC-CH and American Heart Association past president, can comment on smoking's dangers. His number is (919) 966-5201. Dr. Lloyd Chambless of UNC-CH helped with the work. His number is (919) 962-3264.
Contact: David Williamson, (919) 962-8596.
Journal
JAMA