Bigger belly may up smokers' lung cancer risk

Last Updated: 2008-08-19 13:00:25 -0400 (Reuters Health)

By Anne Harding

NEW YORK (Reuters Health) - Smokers who carry more weight around their waistlines may be at greater risk of lung cancer, according to a new study.

The finding, along with the fact that lung cancer risk is actually higher among leaner smokers, provides "intriguing" evidence that how a smoker stores fat could play a role in his or her likelihood of developing lung cancer, Dr. Geoffrey C. Kabat of the Albert Einstein College of Medicine in the Bronx, New York, told Reuters Health.

Several studies have found that a lower body mass index (BMI) means a higher lung cancer risk among smokers. "Reflex explanations" for the link include the fact that smokers are skinnier than non-smokers, Kabat noted in an interview, as well as the tendency for people to gain weight after they quit smoking. Another proposed mechanism for the relationship is that people lose weight when they develop lung cancer.

But careful analysis of the data doesn't bear out these explanations, Kabat said. To better understand the relationship, he and his colleagues looked at data from the Women's Health Initiative.

Over the course of 8 years, 1,365 of the study's 161,809 participants developed lung cancer. When the researchers looked at BMI after adjusting for weight circumference, they found that both smokers and ex-smokers with lower BMIs had a greater lung cancer risk.

But when they looked at waist circumference independent of BMI, they found that a larger waistline conferred a greater likelihood of lung cancer for smokers and ex-smokers. There was no relationship between BMI or waist circumference and lung cancer risk among never-smokers.

The findings, reported in the American Journal of Epidemiology, must be confirmed by other investigators, and don't offer any clues on the mechanism behind the relationship, Kabat noted.

However, he speculated, "it may have to do with the storage, the mobilization, and the metabolization of carcinogens. These carcinogens ... tend to be stored in fat tissue. That may play a role in the development of lung cancer. It may be that it's linked to smoking but that it plays a role on top of smoking."

He added: "We're not ready to give people advice, because overall the advice would not be changed. We're not advocating that people lose weight so that they have a lower risk of lung cancer. Smoking is so far and away the dominant risk factor."

SOURCE: American Journal of Epidemiology, July 15, 2008.

http://www.reutershealth.com/archive/2008/08/19/eline/links/20080819elin002.html