title: Progression from Asthma to Chronic Obstructive Pulmonary Disease. Is Air Pollution a Risk Factor?
abstract: Individuals with asthma-chronic obstructive pulmonary disease (COPD) overlap syndrome (ACOS), have more rapid decline in lung function, more frequent exacerbations, and poorer quality of life than those with asthma or COPD alone. Air pollution exposure is a known risk factor for asthma and COPD; however, its role in ACOS is not as well understood.
  
  
  
  To determine if individuals with asthma exposed to higher levels of air pollution have an increased risk of ACOS.
  
  
  
  Individuals who resided in Ontario, Canada, aged 18 years or older in 1996 with incident asthma between 1996 and 2009 who participated in the Canadian Community Health Survey were identified and followed until 2014 to determine the development of ACOS. Data on exposures to fine particulate matter (PM2.5) and ozone (O3) were obtained from fixed monitoring sites. Associations between air pollutants and ACOS were evaluated using Cox regression models.
  
  
  
  Of the 6,040 adults with incident asthma who completed the Canadian Community Health Survey, 630 were identified as ACOS cases. Compared with those without ACOS, the ACOS population had later onset of asthma, higher proportion of mortality, and more frequent emergency department visits before COPD diagnosis. The adjusted hazard ratios of ACOS and cumulative exposures to PM2.5 (per 10 μg/m(3)) and O3 (per 10 ppb) were 2.78 (95% confidence interval, 1.62-4.78) and 1.31 (95% confidence interval, 0.71-2.39), respectively.
  
  
  
  Individuals exposed to higher levels of air pollution had nearly threefold greater odds of developing ACOS. Minimizing exposure to high levels of air pollution may decrease the risk of ACOS.
authors.affiliation: 1 Child Health Evaluative Sciences, The Hospital for Sick Children, Toronto, Ontario, Canada.|2 Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada.|3 Dalla Lana School of Public Health, Toronto, Ontario, Canada.|4 Institute of Health Policy, Management, and Evaluation and.
authors.forename: Teresa
authors.initials: T
authors.lastname: To
authors.affiliation: 1 Child Health Evaluative Sciences, The Hospital for Sick Children, Toronto, Ontario, Canada.|2 Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada.
authors.forename: Jingqin
authors.initials: J
authors.lastname: Zhu
authors.affiliation: 1 Child Health Evaluative Sciences, The Hospital for Sick Children, Toronto, Ontario, Canada.|4 Institute of Health Policy, Management, and Evaluation and.|5 Department of Geography and Planning, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Kristian
authors.initials: K
authors.lastname: Larsen
authors.affiliation: 1 Child Health Evaluative Sciences, The Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Simatovic
authors.affiliation: 1 Child Health Evaluative Sciences, The Hospital for Sick Children, Toronto, Ontario, Canada.|3 Dalla Lana School of Public Health, Toronto, Ontario, Canada.
authors.forename: Laura
authors.initials: L
authors.lastname: Feldman
authors.affiliation: 1 Child Health Evaluative Sciences, The Hospital for Sick Children, Toronto, Ontario, Canada.|3 Dalla Lana School of Public Health, Toronto, Ontario, Canada.
authors.forename: Kandace
authors.initials: K
authors.lastname: Ryckman
authors.affiliation: 1 Child Health Evaluative Sciences, The Hospital for Sick Children, Toronto, Ontario, Canada.|2 Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada.|4 Institute of Health Policy, Management, and Evaluation and.|6 Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada.
authors.forename: Andrea
authors.initials: A
authors.lastname: Gershon
authors.affiliation: 2 Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada.|7 Department of Medicine, Queen's University, Kingston, Ontario, Canada.
authors.forename: M Diane
authors.initials: MD
authors.lastname: Lougheed
authors.affiliation: 8 Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada.
authors.forename: Christopher
authors.initials: C
authors.lastname: Licskai
authors.affiliation: 2 Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada.|3 Dalla Lana School of Public Health, Toronto, Ontario, Canada.|9 Public Health Ontario, Toronto, Ontario, Canada.
authors.forename: Hong
authors.initials: H
authors.lastname: Chen
authors.affiliation: 3 Dalla Lana School of Public Health, Toronto, Ontario, Canada.|10 CHAIM Research Centre, Carleton University, Ottawa, Ontario, Canada.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Villeneuve
authors.affiliation: 2 Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada.|11 Department of Geography, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Eric
authors.initials: E
authors.lastname: Crighton
authors.affiliation: 12 Ontario Ministry of the Environment and Climate Change, Toronto, Ontario, Canada; and.
authors.forename: Yushan
authors.initials: Y
authors.lastname: Su
authors.affiliation: 13 Institute for Heart and Lung Health, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Mohsen
authors.initials: M
authors.lastname: Sadatsafavi
authors.affiliation: 1 Child Health Evaluative Sciences, The Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: Devon
authors.initials: D
authors.lastname: Williams
authors.affiliation: 13 Institute for Heart and Lung Health, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Christopher
authors.initials: C
authors.lastname: Carlsten
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000397:Air Pollution / Q000009:adverse effects* / Q000706:statistics & numerical data; D001249:Asthma / Q000453:epidemiology*; D015992:Body Mass Index; D018450:Disease Progression; D004781:Environmental Exposure / Q000009:adverse effects / Q000706:statistics & numerical data; D005260:Female; D005500:Follow-Up Studies; D006296:Health Services / Q000706:statistics & numerical data; D006306:Health Surveys; D006801:Humans; D008297:Male; D008875:Middle Aged; D000071069:Multiple Chronic Conditions / Q000453:epidemiology*; D009864:Ontario / Q000453:epidemiology; D010126:Ozone / Q000009:adverse effects; D052638:Particulate Matter / Q000009:adverse effects; D016016:Proportional Hazards Models; D029424:Pulmonary Disease, Chronic Obstructive / Q000453:epidemiology*; D012042:Registries; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects / Q000453:epidemiology; D013577:Syndrome; D055815:Young Adult
chemical_list: D052638:Particulate Matter; D010126:Ozone
keywords: air pollution; coexisting chronic disease morbidities; environmental exposures