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Characteristics of COPD in never-smokers and ever-smokers in the general population: results from the CanCOLD study
  1. W C Tan1,
  2. D D Sin1,
  3. J Bourbeau2,
  4. P Hernandez3,
  5. K R Chapman4,
  6. R Cowie5,
  7. J M FitzGerald6,
  8. D D Marciniuk7,
  9. F Maltais8,
  10. A S Buist9,
  11. J Road6,
  12. J C Hogg1,
  13. M Kirby1,
  14. H Coxson1,
  15. C Hague10,
  16. J Leipsic10,
  17. D E O'Donnell11,
  18. S D Aaron12,
  19. CanCOLD Collaborative Research Group
  1. 1University of British Columbia, Heart Lung Innovation, Vancouver, British Columbia, Canada
  2. 2Respiratory Epidemiology and Clinical Research Unit, Montreal Chest Institute, McGill University Health Centre, McGill University, Montréal, Quebec, Canada
  3. 3Department of Medicine, QEII Health Sciences Centre, Dalhousie University, Halifax, Nova Scotia, Canada
  4. 4Department of Respiratory Medicine, University of Toronto, Toronto, Ontario, Canada
  5. 5Departments of Medicine and Community Health Sciences, University of Calgary, Calgary, Alberta, Canada
  6. 6Department of Respiratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada
  7. 7Department of Respiratory Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
  8. 8Centre de Pneumologie de l'Hopital Laval, Respirology, Quebec City, Quebec, Canada.
  9. 9Oregon Health Sciences University, Portland, Oregon, USA
  10. 10Department of Radiology, St Paul's Hospital, Vancouver, British Columbia, Canada
  11. 11Department of Medicine/Physiology, Queens University, Kingston, Ontario, Canada
  12. 12Ottawa Hospital Research Institute, University of Ottawa, Ottawa, Ontario, Canada
  1. Correspondence to Dr Wan C Tan, UBC James Hogg Research Centre, Providence Heart+Lung Institute, University of British Columbia, St Paul's Hospital, Rm 166, 1081 Burrard Street, Vancouver, British Columbia, Canada V6Z 1Y6; wan.tan{at}


Background There is limited data on the risk factors and phenotypical characteristics associated with spirometrically confirmed COPD in never-smokers in the general population.

Aims To compare the characteristics associated with COPD by gender and by severity of airway obstruction in never-smokers and in ever-smokers.

Method 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.

Trial registration number NCT00920348 (; study ID number: IRO-93326.

  • Clinical Epidemiology
  • COPD epidemiology

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