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WEDNESDAY, Jan. 21 (HealthDayNews) -- If you're a smoker, you might think slashing your pack-a-day habit to just a couple cigarettes a day would proportionately cut your exposure to cancer-causing toxins.

But you'd be wrong.

"For most smokers, the reduction in carcinogen uptake is fairly modest," says Stephen S. Hecht, the Wallin Professor of Cancer Prevention at the University of Minnesota Cancer Center and lead author of a new study that measured lung carcinogen in smokers who tapered off over 26 weeks.

An estimated 440,000 Americans die each year due to smoking-related diseases, says the American Lung Association. Smoking causes 87 percent of lung cancer cases and is responsible for most cases of emphysema and chronic bronchitis, the association reports.

Until now, limited data existed on carcinogen exposure in smokers who reduced their cigarette use without quitting entirely, Hecht and his colleagues note. Their study, published in the Jan. 21 issue of the Journal of the National Cancer Institute, suggests that cutting back is no substitute for quitting.

Smokers "can't necessarily assume they're doing something good for their health," cautions study co-author Dorothy Hatsukami, a professor of psychiatry and director of the University of Minnesota's Transdisciplinary Tobacco Use Research Center. "If you want to improve your health, quitting smoking is the best route to take."

To test the connection between reduced smoking and carcinogen uptake, the Minnesota team measured levels of "metabolites," or human byproducts, of a specific tobacco carcinogen in urine. The carcinogen, called NNK, is found only in tobacco products.

Study volunteers, who smoked an average of 23.7 cigarettes per day, gave two urine samples one week apart before beginning the smoking-reduction program. The participants were expected to pare back the number of cigarettes they smoked per day by 25 percent in the first two weeks, 50 percent in the subsequent two weeks, and 75 percent for the duration of the study. They were offered nicotine replacement products to help them meet those goals.

Urine samples were collected at specific points throughout the 26-week study. The research team measured NNK metabolites as well as levels of anatabine, a compound found in tobacco. Anatabine levels were tracked to verify that patients complied with the protocol.

Overall, the 92 participants who completed treatment experienced statistically significant reductions in lung carcinogen metabolites at most intervals of the smoking reduction program. But those decreases were generally modest and proportionately less than the reduction in cigarettes smoked each day.

"Reducing the number of cigarettes that you smoke is not, for most people, going to give as much of a reduction in carcinogen load as you might have expected," Hecht says.

Even smokers who managed to cut back from an average of 24.7 cigarettes a day to just 2.6 -- a 90 percent reduction -- only reduced their carcinogen dose by 46 percent from baseline levels.

The authors suspect the smokers in the study compensated for the reduced number of cigarettes they lit up each day by changing the way they smoked -- puffing longer and inhaling more deeply.

It's the same reason that so-called "light" cigarettes failed to reduce the health risks of smoking, explains Cheryl G. Healton, president and chief executive officer of the American Legacy Foundation, a Washington, D.C.-based foundation that develops programs to prevent smoking and get people to quit.

"People who use them smoke them in a different way and maintain the same health risks," she says.

The study did not address whether a safer cigarette can be created and whether such a product would reduce the risks to public health, Healton adds.

In an editorial appearing in the same issue of the journal, a team from the National Cancer Institute's Tobacco Control Research Branch questions smoking reduction as a "harm-reduction" strategy. The writers agree with the International Agency for Research on Cancer -- a unit of the World Health Organization -- that the most dramatic health benefits will be achieved in the next half century by boosting the number of smokers who quit.

More information

The American Lung Association has more information on the dangers of smoking and tips on how to quit.

(SOURCES: Stephen S. Hecht, Ph.D., Wallin Professor of Cancer Prevention, University of Minnesota Cancer Center, Minneapolis; Dorothy Hatsukami, Ph.D., professor, psychiatry, adjunct professor, psychology and epidemiology, and director, University of Minnesota's Transdisciplinary Tobacco Use Research Center, Minneapolis; Cheryl G. Healton, Dr. P.H., president and chief executive officer, American Legacy Foundation, Washington, D.C.; Jan. 21, 2004, Journal of the National Cancer Institute)

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