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Study Details Impact of Reducing Smoking on Lung Cancer

Danish doctors report that a heavy smoker who cuts back can lower his or her risk of lung cancer. But they say the risk reduction is not as great as you might think. Still, this may be the best that some smokers can achieve.

Public health studies over the last few years have shown that lung cancer is the leading cause of cancer death worldwide, and about 90 percent of lung cancer cases are tobacco-related.

Getting people who've smoked heavily for decades is very hard, so Danish researchers wondered if just cutting back would protect smokers from lung cancer. The answer is yes, according to their study published in the Journal of American Medical Association.

"There is a significant lowering of lung cancer risk if you cut back on your cigarettes," said physician Nina Godtfredsen of Copenhagen University Hospital.

She and her colleagues came to this conclusion by tracking the smoking habits and health of almost 20,000 people in Denmark for an average of 18 years. But Dr. Godtfredsen notes that the health benefit does not match the amount of smoking reduction.

"A smoker who cuts back on the number of cigarettes by half reduces the risk of lung cancer not by half, but by 25 percent. So the risk is reduced, but not just as much as the number of cigarettes," she explained.

What accounts for this discrepancy? The Danish researcher suggests that smokers who cut back might compensate for the reduced tobacco intake by smoking their remaining cigarettes with more intensity, inhaling deeper and longer.

"If you used to smoke 20 and then you cut back to 10, then you smoke them like you smoked 15 maybe," she added.

A Journal of the American Medical Association editorial accompanying the study says total discontinuation of smoking provides the greatest protection against lung cancer. But it tells physicians to advise patients who cannot quit to cut down as much as possible.

Dr. Godtfredsen sees it this way.

"I think that smoking reduction can be recommended as a step toward smoking cessation," she noted. "But even if the risk of lung cancer is reduced a little bit with smoking reduction, the risk of heart disease and lung disease does not seem to have any benefits from smoking reduction, so I still recommend that people should stop smoking."

A second study in the journal shows the importance of diet in preventing lung cancer. University of Texas researchers linked reduced risk of this disease with higher consumption of some soy products, grains, vegetables, and fruits. These are foods rich in chemicals called phytoestrogens. The six-year study of nearly 3,500 participants indicates that lung cancer risk lowers with increasing phytoestrogen intake.