Decreased Smoking and Lung Cancer Risk

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Summary and Comment

Decreased Smoking and Lung Cancer Risk

A population-based analysis suggests that not only are never smoking and quitting associated with a reduced risk for lung cancer, but so is merely cutting down.

People with histories of minimal or no smoking have markedly reduced risk for lung cancer compared with heavy smokers, but does merely cutting down also reduce risk over time? To answer this question, Danish researchers used data from three longitudinal, population-based cohort studies in which a total of 19,714 adults were followed for as long as 31 years. Subjects were classified into six groups according to past and current smoking status: persistent heavy smokers ( $≥$ 15 cigarettes/day), reducers (heavy smokers who reduced their consumption by $≥$ 50%), light smokers (1–14 cigarettes/day), quitters (stopped smoking during the study period), ex-smokers, and never-smokers.

During a mean follow-up of 18 years, 864 cases of lung cancer were identified. Compared with persistent heavy smokers, all other groups exhibited significantly reduced risk for lung cancer: reducers (hazard ratio, 0.73), quitters (HR, 0.50), light smokers (HR, 0.44), ex-smokers (HR, 0.17), and never-smokers (HR, 0.09).

Comment: Although the smoking data were obtained by self-report, the high level of follow-up and the size of the study population lend support to these findings. The data indicate that not only are never smoking and quitting associated with reduced risk for lung cancer, but so is smoking at a reduced level or cutting down as an adult.

— Thomas L. Schwenk, MD

Published in Journal Watch General Medicine October 4, 2005