Hye Yun Park et al.
The aim of this study was to estimate the risk of lung cancer incidence in never smokers with COPD, and to compare it with the risk associated with smoking. This cohort study involved 338 548 subjects, 40 to 84 years of age with no history of lung cancer at baseline, enrolled in the National Health Insurance Service National Sample Cohort.
Compared with never smokers without COPD, the fully-adjusted hazard ratios (95% CI) for lung cancer in never smokers with COPD, ever smokers without COPD, and ever smokers with COPD were 2.67 (2.09 to 3.40), 1.97 (1.75 to 2.21), and 6.19 (5.04 to 7.61), respectively.
COPD was a strong independent risk factor for lung cancer incidence in never smokers. A clear limitation of the study was they they did not have information on environmental/occupational exposures or severity of emphysema, which could be potential confounders for increased lung cancer risk in COPD.