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Original research
Short-term air pollution exposure and exacerbation events in mild to moderate COPD: a case-crossover study within the CanCOLD cohort
  1. Bryan A Ross1,2,
  2. Dany Doiron1,
  3. Andrea Benedetti1,
  4. Shawn D Aaron3,
  5. Kenneth Chapman4,
  6. Paul Hernandez5,
  7. François Maltais6,
  8. Darcy Marciniuk7,
  9. Denis E O'Donnell8,
  10. Don D Sin9,
  11. Brandie L Walker10,
  12. Wan Tan9,
  13. Jean Bourbeau1,2
  14. for the CanCOLD Collaborative Research Group and the Canadian Respiratory Research Network
  1. 1 Respiratory Epidemiology and Clinical Research Unit, Centre for Outcomes Research and Evaluation, Research Institute of the McGill University Health Centre, Montreal, Québec, Canada
  2. 2 Medicine, McGill University Health Centre, Montreal, Québec, Canada
  3. 3 The Ottawa Hospital Research Institute, University of Ottawa, Ottawa, Ontario, Canada
  4. 4 Toronto General Hospital Research Institute, University of Toronto, Toronto, Ontario, Canada
  5. 5 Medicine, Dalhousie University Faculty of Medicine, Halifax, Nova Scotia, Canada
  6. 6 Institut universitaire de cardiologie et de pneumologie de Québec, Université Laval, Québec, Québec, Canada
  7. 7 Respiratory Research Centre, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
  8. 8 Medicine, Queens University, Kingston, Ontario, Canada
  9. 9 Centre for Heart Lung Innovation, St. Paul's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
  10. 10 Medicine, University of Calgary, Calgary, Alberta, Canada
  1. Correspondence to Dr Jean Bourbeau, McGill University, Montreal, Canada; jean.bourbeau{at}


Background Infections are considered as leading causes of acute exacerbations of chronic obstructive pulmonary disease (COPD). Non-infectious risk factors such as short-term air pollution exposure may play a clinically important role. We sought to estimate the relationship between short-term air pollutant exposure and exacerbations in Canadian adults living with mild to moderate COPD.

Methods In this case-crossover study, exacerbations (‘symptom based’: ≥48 hours of dyspnoea/sputum volume/purulence; ‘event based’: ‘symptom based’ plus requiring antibiotics/corticosteroids or healthcare use) were collected prospectively from 449 participants with spirometry-confirmed COPD within the Canadian Cohort Obstructive Lung Disease. Daily nitrogen dioxide (NO2), fine particulate matter (PM2.5), ground-level ozone (O3), composite of NO2 and O3 (Ox), mean temperature and relative humidity estimates were obtained from national databases. Time-stratified sampling of hazard and control periods on day ‘0’ (day-of-event) and Lags (‘−1’ to ‘−6’) were compared by fitting generalised estimating equation models. All data were dichotomised into ‘warm’ (May–October) and ‘cool’ (November–April) seasons. ORs and 95% CIs were estimated per IQR increase in pollutant concentrations.

Results Increased warm season ambient concentration of NO2 was associated with symptom-based exacerbations on Lag−3 (1.14 (1.01 to 1.29), per IQR), and increased cool season ambient PM2.5 was associated with symptom-based exacerbations on Lag−1 (1.11 (1.03 to 1.20), per IQR). There was a negative association between warm season ambient O3 and symptom-based events on Lag−3 (0.73 (0.52 to 1.00), per IQR).

Conclusions Short-term ambient NO2 and PM2.5 exposure were associated with increased odds of exacerbations in Canadians with mild to moderate COPD, further heightening the awareness of non-infectious triggers of COPD exacerbations.

  • COPD exacerbations
  • COPD exacerbations mechanisms
  • COPD epidemiology
  • Clinical epidemiology

Data availability statement

Data are available upon reasonable request.

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Data availability statement

Data are available upon reasonable request.

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  • Collaborators CanCOLD Collaborative Research Group and Canadian Respiratory Research Network.

  • Contributors BAR, DD and JB developed the protocol, analysed the data and drafted the original version of the manuscript. BAR, DD, AB, SDA, KC, PH, FM, DM, DEO'D, DDS, BLW, WT and JB made substantial contributions to the design of the study, interpretation of the data, revision of the manuscript for important intellectual content and approved the final version submitted for publication. All authors have given agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the study are appropriately investigated and resolved. JB is the guarantor for the study. JB accepts full responsibility for the finished work and/or the conduct of the study, had access to the data, and controlled the decision to publish.

  • Funding The Canadian Cohort Obstructive Lung Disease (CanCOLD; NCT00920348) study is currently funded by the Canadian Respiratory Research Network and the industry partners AstraZeneca Canada Ltd, Boehringer Ingelheim Canada Ltd, GlaxoSmithKline (GSK) Canada Ltd, and Novartis. Researchers at RI-McGill University Health Centre Montreal and iCAPTURE Centre Vancouver lead the project. Previous funding partners were the Canadian Institutes of Health Research (CIHR; CIHR/Rx&D Collaborative Research Program Operating Grants- 93326), the Respiratory Health Network of the Fonds de la recherche en santé du Québec (FRQS), and industry partners: Almirall; Merck Nycomed; Pfizer Canada Ltd; and Theratechnologies. This work was supported with funding from the Canadian Institutes of Health Research (CIHR: #453225) and the Réseau en Santé Respiratoire du FRQS (RSRQ).

  • Competing interests BAR reports grants/contracts from the Canadian Institutes of Health Research (CIHR), Réseau de Recherche en Santé Respiratoire du Québec (RSRQ), Research Institute of the MUHC (RI MUHC), Ministère de l'Économie et de l'Innovation (MEI) Québec, McGill University Health Centre (MUHC) Foundation Grant, Fonds de Recherche Santé Québec (FRSQ), and CHEST Foundation Grant; and payments/honoraria from the Canadian Thoracic Society (CTS), CHEST/ACCP, Respiplus (non-profit), Alberta Kinesiology Association (AKA), and McGill University Continuing Professional Development (CPD). SDA reports payments/honoraria from AstraZeneca, GSK; and participation on Data Safety Monitoring/Advisory Board for AstraZeneca, GSK, and Sanofi. PH reports grants/contracts from Boehringer Ingelheim, Cyclomedica, Grifols, Vertex; consulting fees from Acceleron, AstraZeneca, Boehringer Ingelheim, Covis, GlaxoSmithKline, Janssen, Novartis, Sanofi, Teva, Takeda, Valeo; and leadership/fiduciary role in the Canadian Thoracic Society. FM reports grants/contracts from GlaxoSmithKline, AstraZeneca, Sanofi, Novartis, Boehringer Ingelheim, Grifols; consulting fees from AstraZeneca; payment/honoraria from GlaxoSmithKline, Boehringer Ingelheim, Grifols, Novartis; and stock/stock options from Oxynov. DM reports grants/contracts from AstraZeneca, Boehringer Ingelheim, Canadian Institute of Health Research, GlaxoSmithKline, Grifols, Lung Association—Saskatchewan, Novartis, Sanofi, Saskatchewan Health Research Foundation, Schering-Plough; consulting fees from Alberta Health Services, Canadian Foundation for Healthcare Improvement, Health Canada, Lung Association—Saskatchewan, Ontario Ministry of Health and Long-Term Care, Saskatchewan Health Authority, Yukon Health and Social Services; payment/honoraria from the Lung Association—Saskatchewan, American College of Chest Physicians; leadership/fiduciary role in the CHEST journal, Canadian Thoracic Society, American Thoracic Society and AARC; and is an employee of the University of Saskatchewan. DE O’D reports grants/contracts from AstraZeneca, Lung Health Foundation and Boehringer Ingelheim Canada; and payment/honoraria from GSK and Viajes Pacifico. BLW reports payment/honoraria from AstraZeneca, GSK, Sanofi; and Data Safety Monitoring/Advisory Board participation for AstraZeneca, GSK, and Sanofi. JB reports grants/contracts from the Canadian Institute of Health Research (CIHR), Réseau en santé respiratoire du FRQS, McGill University, McGill University Health Centre Foundation, AstraZeneca Canada Ltd, Boehringer Ingelheim Canada Ltd, GSK, Grifols, Novartis, Sanofil, Trudell Canada Ltd; and payment/honoraria from AstraZeneca Canada Ltd, Boehringer Ingelheim Canada Ltd, GSK, Pfizer Canada Ltd, and Trudell Canada Ltd.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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