Differences in chronic obstructive pulmonary disease phenotypes between non-smokers and smokers.
OBJECTIVE
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 phenotypes 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 = 49) had younger patients and had a greater BMI than the smoker group (n = 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 = .051). In the subgroup of biomass smoke-exposed subjects, MWA% was significantly greater in smokers than in non-smokers (MWA 69.1 vs. 65.3, P = .03), while EI was not statistically different (EI 7.1 vs. 10.4, P = .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 significant interaction with tobacco smoking in an airway-predominant phenotype.
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.
Wonjun
W
Ji
Department of Respiratory Center, Kangwon National University Hospital, 156, Baengyeong-ro, Chuncheon-si, Gangwon-do, Korea.
Myoung Nam
MN
Lim
Department of Radiology, Kangwon National University Hospital, 156, Baengyeong-ro, Chuncheon-si, Gangwon-do, Korea.
So Hyeon
SH
Bak
Department of Internal Medicine and Environmental Health Center, Kangwon National University Hospital, 156, Baengyeong-ro, Chuncheon-si, Gangwon-do, Korea.
Seok-Ho
SH
Hong
Department of Internal Medicine and Environmental Health Center, Kangwon National University Hospital, 156, Baengyeong-ro, Chuncheon-si, Gangwon-do, Korea.
Seon-Sook
SS
Han
Department of Internal Medicine and Environmental Health Center, Kangwon National University Hospital, 156, Baengyeong-ro, Chuncheon-si, Gangwon-do, Korea.
Seung-Joon
SJ
Lee
Department of Internal Medicine and Environmental Health Center, Kangwon National University Hospital, 156, Baengyeong-ro, Chuncheon-si, Gangwon-do, Korea.
Woo Jin
WJ
Kim
Department of Internal Medicine and Environmental Health Center, Kangwon National University Hospital, 156, Baengyeong-ro, Chuncheon-si, Gangwon-do, Korea.
Yoonki
Y
Hong
D000367:Age Factors; D000368:Aged; D003430:Cross-Sectional Studies; D005069:Evaluation Studies as Topic; D005541:Forced Expiratory Volume; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D010641:Phenotype; D015995:Prevalence; D029424:Pulmonary Disease, Chronic Obstructive / Q000000981:diagnostic imaging* / Q000453:epidemiology* / Q000235:genetics; D012016:Reference Values; D056910:Republic of Korea / Q000453:epidemiology; D012307:Risk Factors; D012720:Severity of Illness Index; D012907:Smoking / Q000009:adverse effects*; D013147:Spirometry / Q000379:methods; D018709:Statistics, Nonparametric; D015996:Survival Rate; D014057:Tomography, X-Ray Computed / Q000379:methods*
airway disease; chronic obstructive pulmonary disease; emphysema; non-smoker; smoker