title: Characteristics of COPD in never-smokers and ever-smokers in the general population: results from the CanCOLD study.
abstract: BACKGROUND
  There is limited data on the risk factors and phenotypical characteristics associated with spirometrically confirmed COPD in never-smokers in the general population.
  
  
  OBJECTIVE
  To compare the characteristics associated with COPD by gender and by severity of airway obstruction in never-smokers and in ever-smokers.
  
  
  METHODS
  We analysed the data from 5176 adults aged 40 years and older who participated in the initial cross-sectional phase of the population-based, prospective, multisite Canadian Cohort of Obstructive Lung Disease study. Never-smokers were defined as those with a lifetime exposure of <1/20 pack year. Logistic regressions were constructed to evaluate associations for 'mild' and 'moderate-severe' COPD defined by FEV1/FVC <5th centile (lower limits of normal). Analyses were performed using SAS V.9.1 (SAS Institute, Cary, North Carolina, USA).
  
  
  RESULTS
  The prevalence of COPD (FEV1/FVC<lower limits of normal) in never-smokers was 6.4%, constituting 27% of all COPD subjects. The common independent predictors of COPD in never-smokers and ever-smokers were older age, self reported asthma and lower education. In never-smokers a history of hospitalisation in childhood for respiratory illness was discriminative, while exposure to passive smoke and biomass fuel for heating were discriminative for women. COPD in never-smokers and ever-smokers was characterised by increased respiratory symptoms, 'respiratory exacerbation' events and increased residual volume/total lung capacity, but only smokers had reduced DLCO/Va and emphysema on chest CT scans.
  
  
  CONCLUSIONS
  The study confirmed the substantial burden of COPD among never-smokers, defined the common and gender-specific risk factors for COPD in never-smokers and provided early insight into potential phenotypical differences in COPD between lifelong never-smokers and ever-smokers.
  
  
  BACKGROUND
  NCT00920348 (ClinicalTrials.gov); study ID number: IRO-93326.
authors.affiliation: University of British Columbia, Heart Lung Innovation, Vancouver, British Columbia, Canada.
authors.forename: W C
authors.initials: WC
authors.lastname: Tan
authors.affiliation: University of British Columbia, Heart Lung Innovation, Vancouver, British Columbia, Canada.
authors.forename: D D
authors.initials: DD
authors.lastname: Sin
authors.affiliation: Respiratory Epidemiology and Clinical Research Unit, Montreal Chest Institute, McGill University Health Centre, McGill University, Montréal, Quebec, Canada.
authors.forename: J
authors.initials: J
authors.lastname: Bourbeau
authors.affiliation: Department of Medicine, QEII Health Sciences Centre, Dalhousie University, Halifax, Nova Scotia, Canada.
authors.forename: P
authors.initials: P
authors.lastname: Hernandez
authors.affiliation: Department of Respiratory Medicine, University of Toronto, Toronto, Ontario, Canada.
authors.forename: K R
authors.initials: KR
authors.lastname: Chapman
authors.affiliation: Departments of Medicine and Community Health Sciences, University of Calgary, Calgary, Alberta, Canada.
authors.forename: R
authors.initials: R
authors.lastname: Cowie
authors.affiliation: Department of Respiratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: J M
authors.identifier: http://orcid.org/0000-0002-0419-7862
authors.initials: JM
authors.lastname: FitzGerald
authors.affiliation: Department of Respiratory Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
authors.forename: D D
authors.initials: DD
authors.lastname: Marciniuk
authors.affiliation: Centre de Pneumologie de l'Hopital Laval, Respirology, Quebec City, Quebec, Canada.
authors.forename: F
authors.initials: F
authors.lastname: Maltais
authors.affiliation: Oregon Health Sciences University, Portland, Oregon, USA.
authors.forename: A S
authors.initials: AS
authors.lastname: Buist
authors.affiliation: Department of Respiratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: J
authors.initials: J
authors.lastname: Road
authors.affiliation: University of British Columbia, Heart Lung Innovation, Vancouver, British Columbia, Canada.
authors.forename: J C
authors.initials: JC
authors.lastname: Hogg
authors.affiliation: University of British Columbia, Heart Lung Innovation, Vancouver, British Columbia, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Kirby
authors.affiliation: University of British Columbia, Heart Lung Innovation, Vancouver, British Columbia, Canada.
authors.forename: H
authors.initials: H
authors.lastname: Coxson
authors.affiliation: Department of Radiology, St Paul's Hospital, Vancouver, British Columbia, Canada.
authors.forename: C
authors.initials: C
authors.lastname: Hague
authors.affiliation: Department of Radiology, St Paul's Hospital, Vancouver, British Columbia, Canada.
authors.forename: J
authors.initials: J
authors.lastname: Leipsic
authors.affiliation: University of British Columbia, Heart Lung Innovation, Vancouver, British Columbia, Canada Respiratory Epidemiology and Clinical Research Unit, Montreal Chest Institute, McGill University Health Centre, McGill University, Montréal, Quebec, Canada Department of Medicine, QEII Health Sciences Centre, Dalhousie University, Halifax, Nova Scotia, Canada Department of Respiratory Medicine, University of Toronto, Toronto, Ontario, Canada Departments of Medicine and Community Health Sciences, University of Calgary, Calgary, Alberta, Canada Department of Respiratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada Department of Respiratory Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada Centre de Pneumologie de l'Hopital Laval, Respirology, Quebec City, Quebec, Canada. Oregon Health Sciences University, Portland, Oregon, USA Department of Radiology, St Paul's Hospital, Vancouver, British Columbia, Canada Department of Medicine/Physiology, Queens University, Kingston, Ontario, Canada Ottawa Hospital Research Institute, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: D E
authors.initials: DE
authors.lastname: O'Donnell
authors.affiliation: Ottawa Hospital Research Institute, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: S D
authors.initials: SD
authors.lastname: Aaron
mesh_terms: D000328:Adult; D000368:Aged; D000402:Airway Obstruction / Q000503:physiopathology*; D002170:Canada; D003430:Cross-Sectional Studies; D005260:Female; D006760:Hospitalization; D006801:Humans; D016015:Logistic Models; D008168:Lung / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D011446:Prospective Studies; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology*; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects*; D014028:Tobacco Smoke Pollution / Q000009:adverse effects*
chemical_list: D014028:Tobacco Smoke Pollution
keywords: COPD epidemiology; Clinical Epidemiology