Chronic obstructive pulmonary disease and lung cancer incidence in never smokers: a cohort study

Abstract

There has been limited evidence for the association between chronic obstructive pulmonary disease (COPD) and the incidence of lung cancer among never smokers. We aimed 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. During 2 355 005 person-years of follow-up (median follow-up 7.0 years), 1834 participants developed lung cancer. 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. In this large national cohort study, COPD was also a strong independent risk factor for lung cancer incidence in never smokers, implying that COPD patients are at high risk of lung cancer, irrespective of smoking status.

Keywords: COPD; lung cancer; never smokers.

Figure 1

Cumulative incidence function for lung cancer by chronic obstructive pulmonary disease (COPD) and smoking status. COPD was considered as a time-varying exposure. Unexposed person-time was contributed by participants who did not develop COPD and by participants who developed lung cancer before COPD development. Cumulative incidence functions take into account competing risks from all-cause mortality.