title: Chronic obstructive pulmonary disease in non-smokers: a case-comparison study.
abstract: BACKGROUND
  COPD is often regarded as a smoker's disease. In fact, up to 50% of COPD could be attributable to other causes. Relatively little is known about COPD among nonsmokers, and this group is usually excluded from studies of COPD.
  
  
  METHODS
  In this cross-sectional case-comparison study, smokers and nonsmokers aged over 45 with COPD (post-bronchodilator FEV1 ≤ 70% predicted, FEV1/FVC ratio < 0.7) were recruited from specialist outpatient clinics and from primary care. Subjects completed a questionnaire and interview, and underwent spirometry, venesection, exhaled nitric oxide (ENO) measurement, allergen skinprick testing, formal lung function testing and high resolution CT.
  
  
  RESULTS
  48 nonsmokers and 45 smokers participated. Asthma was nearly universal among nonsmokers and was the commonest identifiable cause of COPD in that group. Nonsmokers also exhibited a high prevalence of objective eosinophilic inflammation (raised ENO and eosinophil counts, positive skinprick tests). Smokers had more severe airflow obstruction, but respiratory symptom prevalences were similar between groups. Nonsmokers reported greater lifetime burdens of respiratory disease. Nonsmokers' HRCT results showed functional small airways disease, with no significant emphysema in any subject. Previously undiagnosed bronchiectasis was common in both groups (31% and 42%).
  
  
  CONCLUSIONS
  Asthma is a very common cause of COPD among nonsmokers. Radiological bronchiectasis is common in COPD; the clinical significance of this finding is unclear.
authors.affiliation: 1Department of Medicine, University of Auckland , Auckland , New Zealand.
authors.forename: Paul
authors.initials: P
authors.lastname: Sexton
authors.forename: Peter
authors.initials: P
authors.lastname: Black
authors.forename: Lian
authors.initials: L
authors.lastname: Wu
authors.forename: Fay
authors.initials: F
authors.lastname: Sommerville
authors.forename: Maye
authors.initials: M
authors.lastname: Hamed
authors.forename: David
authors.initials: D
authors.lastname: Milne
authors.forename: Patricia
authors.initials: P
authors.lastname: Metcalf
authors.forename: John
authors.initials: J
authors.lastname: Kolbe
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001249:Asthma / Q000453:epidemiology* / Q000503:physiopathology; D001944:Breath Tests; D001987:Bronchiectasis / Q000000981:diagnostic imaging / Q000453:epidemiology* / Q000503:physiopathology; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D004802:Eosinophilia / Q000453:epidemiology*; D005260:Female; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009569:Nitric Oxide / Q000378:metabolism; D029424:Pulmonary Disease, Chronic Obstructive / Q000000981:diagnostic imaging / Q000453:epidemiology* / Q000503:physiopathology; D012307:Risk Factors; D012720:Severity of Illness Index; D012882:Skin Tests; D012907:Smoking / Q000453:epidemiology*; D013147:Spirometry; D014057:Tomography, X-Ray Computed
chemical_list: D009569:Nitric Oxide