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.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).
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.
Reference:
Godtfredsen NS et al. Effect of smoking reduction on lung cancer risk. JAMA 2005 Sep 28; 294:1505-10.