ORIGINAL ARTICLE Differences in chronic obstructive pulmonary disease phenotypes between non-smokers and smokers Wonjun Ji 1 | Myoung Nam Lim 2 | So Hyeon Bak 3 | Seok-Ho Hong 4 | Seon-Sook Han 4 | Seung-Joon Lee 4 | Woo Jin Kim 4 | Yoonki Hong 4 1 Department of Pulmonary and Critical Care Medicine, Asan Medical Center, University of Ulsan College of Medicine, 88, Olympic-ro 43-gil, Songpa-gu, Seoul, Korea 2 Department of Respiratory Center, Kangwon National University Hospital, 156, Baengyeong-ro, Chuncheon-si, Gangwon-do, Korea 3 Department of Radiology, Kangwon National University Hospital, 156, Baengyeong-ro, Chuncheon-si, Gangwon-do, Korea 4 Department of Internal Medicine and Environmental Health Center, Kangwon National University Hospital, 156, Baengyeong-ro, Chuncheon-si, Gangwon-do, Korea Correspondence Yoonki Hong, M.D., Department of Internal Medicine and Environmental Health Center, Kangwon National University Hospital, 156, Baengnyeong-ro, Chuncheon-si, Gangwon-do, Chuncheon, Korea. Email: h-doctor@hanmail.net Funding information This study was supported by a grant from the Ministry of Environment, Republic of Korea. Abstract Introduction and Objectives: Although tobacco smoking is a major risk factor for chronic obstructive pulmonary disease (COPD), more than one-fourth of COPD patients are non-smokers. In this cross-sectional study, the differences in COPD phe- notypes between non-smokers and smokers in male subjects were investigated and were focused on structural lung changes using a quantitative assessment of computed tomography (CT) images. Methods: They divided male participants with COPD, from a Korean cohort near a cement plant, into non-smokers and smokers by a cutoff of a 5 pack-year smoking history. Clinical characteristics, including age, body mass index (BMI), spirometry results, history of biomass smoke exposure, and CT measurements, were compared between the two groups. Emphysema index (EI) and mean wall area percentage (MWA %) were used to evaluate the structural lung changes on volumetric CT scans. Results: The non-smoker group (n 5 49) had younger patients and had a greater BMI than the smoker group (n 5 113) (P < .05). Spirometry results, including post- bronchodilator forced expiratory volume in 1 s, were comparable between the two groups. More smokers had emphysema than non-smokers (EI 10.0 vs. 6.5, P < .001), but after accounting the potential confounders in model analysis, the difference was borderline significance (P 5 .051). In the subgroup of biomass smoke-exposed sub- jects, MWA% was significantly greater in smokers than in non-smokers (MWA 69.1 vs. 65.3, P 5 .03), while EI was not statistically different (EI 7.1 vs. 10.4, P 5 .52). Conclusions: Non-smoker males with COPD were younger and had a greater BMI than the smokers. Tobacco smoke exposure seemed to be associated with an emphysema-predominant phenotype, while biomass smoke exposure exhibited a sig- nificant interaction with tobacco smoking in an airway-predominant phenotype. KEYWORDS airway disease, chronic obstructive pulmonary disease, emphysema, non-smoker, smoker Abbreviations: BDR, bronchodilator response; BMI, body mass index; CAT, COPD Assessment Test; COPD, chronic obstructive pulmonary disease; CT, computed tomography; EI, Emphysema index; FEV1, forced expiratory volume in 1 sec; FVC, forced vital capacity; HU, Hounsfield Units; LA, lumen area; MDI, metered-dose inhaler; MLD, mean lung density; mMRC, modified Medical Research Council; MWA%, mean wall area percentage; SD, standard deviation; WA, wall area. Clin. Respir. J. 2016; 1-8 wileyonlinelibrary.com/journal/crj V C 2016 John Wiley & Sons Ltd | 1 Received: 6 June 2016 | Revised: 5 October 2016 | Accepted: 25 October 2016 DOI 10.1111/crj.12577