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Smoking less may not cut risk after all

cigarette butts

Smokers who cut back tend to draw more deeply on the fewer cigarettes they smoke (NIEHS)

Cutting down on smoking may not lower your risk of cancer, a controversial U.S. study suggests.

The results of the study, led by Dr Stephen Hecht from the University of Minnesota Cancer Center in Minneapolis, were published in today's Journal of the National Cancer Institute.

As expected, smoking fewer cigarettes lowered smokers' exposure to a particular carcinogen found in tobacco. But that decrease was only brief and not in proportion to the amount smokers cut back.

The researchers suggested that smokers who cut back tend to inhale more deeply on the cigarettes they have, exposing themselves to higher levels of cancer causing chemicals than previously thought.

A total of 153 people who smoked an average of about 23 cigarettes a day took part in the study. The researchers assigned 102 participants to a quit group and tried to cut the amount of tobacco they smoked by 75% over six weeks. The smokers were then asked to stick with this level of smoking for another 20 weeks. They could use nicotine patches or gum to help them but back.

The researchers measured levels of NNL, a strong carcinogen found in tobacco, initially and at weeks 4, 6, 8, 12 and 26.

Compared to the smokers who didn't cut back, the quit group were exposed to less of the carcinogen, but not in proportion to the number of cigarettes they had given up.

"The results indicate that some smokers may benefit from reduced smoking, but for most the effects are modest, probably due to compensation," the researchers said.

Fewer than 30 of the quit group of 102 could maintain the 70% reduction in how much they smoked over 12 weeks. This equated to about a 50% reduction in total NNAL, they said.

The researchers suggested that when giving up smoking, levels of the carcinogen rather than the number of cigarettes smoked a day may be a better indicator of the effective lowering of a person's cancer risk.

Australian researcher Renee Bittoun director of the smoking research unit at the University of Sydney said that the results were interesting but not surprising.

"It shows that cutting down is not advisable. Cutting out is the answer. There is no safe level.

"It's ironic but if you smoke a stronger cigarette you're less likely to inhale it deeper, although the nicotine concentration is a problem. [Whether you are talking about smoking] a light cigarette or less cigarettes, the principle is exactly the same. You are doing to draw back cigarettes deeper. If anything the answer might be [smoking] a stronger one."

Bittoun questioned the use of nicotine replacement therapy in the study, although she said it was difficult for smokers to drastically cut down without it.

"Nicotine isn't benign. This is the flaw in the study," Bittoun told ABC Science Online. "I think it's a bit of a confounder because nicotine is a carcinogen too."

Tags: health, science-and-technology, biology