Thorax 65:612-618 doi:10.1136/thx.2009.131078
  • Asthma

Burden of comorbidity in individuals with asthma

  1. Teresa To2
  1. 1Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada
  2. 2The Hospital For Sick Children, Toronto, Ontario, Canada
  1. Correspondence to Dr Andrea Gershon, Institute for Clinical Evaluative Sciences, G1 06, 2075 Bayview Avenue, Toronto Ontario, M4N 3M5, Canada; andrea.gershon{at}
  • Received 12 November 2009
  • Accepted 11 April 2010


Background and aims Asthma comorbidity, such as depression and obesity, has been associated with greater healthcare use, decreased quality of life and poor asthma control. Treating this comorbidity has been shown to improve asthma outcomes as well as overall health. Despite this, asthma comorbidity remains relatively under-recognised and understudied—perhaps because most asthma occurs in young people who are believed to be healthy and relatively free of comorbidity. The aim of this study was to quantify empirically the amount of comorbidity associated with asthma.

Methods A population-based cohort study was conducted using the health administrative data of the 12 million residents of Ontario, Canada in 2005. A validated health administrative algorithm was used to identify individuals with asthma.

Results The amount of comorbidity among individuals with asthma, as reflected in rates of hospitalisations, emergency department visits and ambulatory care claims, was found to be substantial and much greater than that observed among individuals without asthma. Together, asthma and asthma comorbidity (the extra comorbidity found in individuals with asthma compared with those without asthma) were associated with 6% of all hospitalisations, 9% of all emergency room visits and 6% of all ambulatory care visits that occurred in Ontario.

Conclusions Asthma comorbidity places a significant burden on individuals and the healthcare system and should be considered in the management of asthma. Further research should focus on which types of asthma comorbidity are responsible for the greatest burden and how such comorbidity should be prevented and managed.


  • Funding ASG is supported by a Career Scientist Award from the Ontario Ministry of Health and Long Term Care, and was supported by a Research Fellowship from the Canadian Institutes of Health Research, Institute of Population and Public Health and The Public Health Agency of Canada while working on this study. TT is supported by The Dales Award in Medical Research from the University of Toronto, Toronto, Ontario, Canada. Funding for this project was made available through the Canadian Institutes of Health Research (PHE - 85212); Government of Ontario; and the Public Health Agency of Canada who had no role in study design, collection, analysis, interpretation of data, writing of the report or in the decision to submit the report for publication. This study was also supported by the Institute for Clinical Evaluative Sciences (ICES), which is funded by an annual grant from the Ontario Ministry of Health and Long-Term Care. The opinions, results and conclusions reported in this paper are those of the authors and are independent from the funding sources. No endorsement by ICES or any of the funding sources is intended or should be inferred and none had any role in study design, collection, analysis, interpretation of data, writing of the report, or in the decision to submit the report for publication.

  • Competing interests None.

  • Ethics approval This study was conducted with the approval of the The Hospital for Sick Children and Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada.

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

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