Rationale: 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. Objectives: To determine if individuals with asthma exposed to higher levels of air pollution have an increased risk of ACOS. Methods: 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.Dataonexposuresto fineparticulatematter(PM2.5) andozone (O3) were obtained from fixed monitoring sites. Associations between air pollutants and ACOS were evaluated using Cox regression models. Measurements and Main Results: Of the 6,040 adults with incident asthmawhocompletedtheCanadianCommunityHealthSurvey,630were identifiedasACOScases.ComparedwiththosewithoutACOS,theACOS 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/m3) 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. Conclusions: Individuals exposed to higher levels of air pollution had nearly threefold greater odds of developing ACOS. Minimizing exposuretohighlevelsofairpollutionmaydecreasetheriskofACOS.

Additional Metadata
Keywords Air pollution, Coexisting chronic disease morbidities, Environmental exposures
Persistent URL dx.doi.org/10.1164/rccm.201510-1932OC
Journal American Journal of Respiratory and Critical Care Medicine
To, T. (Teresa), Zhu, J. (Jingqin), Larsen, K. (Kristian), Simatovic, J. (Jacqueline), Feldman, L. (Laura), Ryckman, K. (Kandace), … Carlsten, C. (Christopher). (2016). Progression from asthma to chronic obstructive pulmonary disease is air pollution a risk factor?. American Journal of Respiratory and Critical Care Medicine, 194(4), 429–438. doi:10.1164/rccm.201510-1932OC