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Patients with COPD and chronic asthma at higher risk of severe illness: Ontario study


A study from the Institute for Clinical Evaluative Sciences (ICES) and Sunnybrook Health Sciences Centre has shed new light on the relationship between asthma and chronic obstructive pulmonary disease (COPD), showing that people with COPD are 53 per cent more likely to be hospitalized if they have a history of asthma.

“This study suggests that people with a history of asthma are at a higher risk of serious COPD-related complications, particularly if their asthma has been poorly controlled,” says Dr. Tetyana Kendzerska, the lead author of the paper who is a postdoctoral fellow at ICES and Sunnybrook Health Sciences Centre. “This study provides robust evidence about the relationship between chronic asthma and COPD that we have previously lacked for prognosis.”

Chronic obstructive pulmonary disease (COPD) is a common and debilitating lung disease in people age 40 and older that causes obstructed airflow due to irreparable lung tissue damage. While COPD patients experience some symptoms that can be confused with asthma, the two diseases have very different disease mechanisms and their treatment strategies sometimes conflict. People with well-managed asthma can have normal lung function, but damage from COPD is largely unrecoverable.

The researchers say that while overlapping diagnoses of both asthma and COPD are fairly common, the relationship between the two diseases has been under-investigated to date. They say previous work has been limited by small study size and the difficulty in accounting for timing in the onset of the two diseases, as well as tracking patient outcomes over long periods of time.

This new study took advantage of the robust population health data securely housed at ICES to examine long-term health outcomes in approximately 9,053 middle-aged people (age 40-55) with physician-diagnosed COPD. It found that 30 per cent (or 2,717) of these patients had a previous diagnosis of asthma. The researchers then compared their health outcomes over time with the COPD patients with no history of asthma.

Over a median follow-up time of about three years, 282 of 2,717 (10.4 per cent) individuals with COPD and a history of asthma and 430 of 6,336 (6.8 per cent) with COPD and without a history of asthma were hospitalized with COPD. After adjusting for age and possible misclassification factors, the study found that COPD patients with a history of asthma were 53 per cent more likely to be hospitalized for COPD. Individuals with more severe asthma did worse than those with milder asthma.

The impact could be seen regardless of the patient’s history of smoking.

The authors note that while it is not possible based on this study to make a direct causal link between chronic asthma and COPD, the data do point to a relationship.

“Our previous work shows that one in three Ontarians will be diagnosed with asthma in their lifetimes,” says Dr. Andrea Gershon, the senior author on the paper who is a physician at Sunnybrook Health Sciences Centre and who leads the Lung Health Program at ICES. “Awareness that people with asthma are at increased risk of developing COPD means that care providers can work with their patients to optimize their asthma care and preserve their lung function as they age.”

The study was produced in collaboration with the Canadian Respiratory Research Network.

“The impact of a history of asthma on long-term outcomes of people with newly diagnosed chronic obstructive pulmonary disease: a population study” was published today in the Journal of Allergy and Clinical Immunology.

Author block: Kendzerska T, To TM, Aaron SD, Lougheed MD, Sadatsafavi M, FitzGerald JM, Gershon AS.

The Institute for Clinical Evaluative Sciences (ICES) is an independent, non-profit organization that uses population-based health information to produce knowledge on a broad range of healthcare issues. Our unbiased evidence provides measures of health system performance, a clearer understanding of the shifting healthcare needs of Ontarians, and a stimulus for discussion of practical solutions to optimize scarce resources. ICES knowledge is highly regarded in Canada and abroad, and is widely used by government, hospitals, planners, and practitioners to make decisions about care delivery and to develop policy. For the latest ICES news, follow us on Twitter: @ICESOntario

Sunnybrook Health Sciences Centre is inventing the future of healthcare for the 1.2 million patients the hospital cares for each year through the dedication of its more than 10,000 staff and volunteers. An internationally recognized leader in research and education and a full affiliation with the University of Toronto distinguishes Sunnybrook as one of Canada’s premier academic health sciences centres. Sunnybrook specializes in caring for high-risk pregnancies, critically-ill newborns and adults, offering specialized rehabilitation and treating and preventing cancer, cardiovascular disease, neurological and psychiatric disorders, orthopaedic and arthritic conditions and traumatic injuries. The Hospital also has a unique and national leading program for the care of Canada’s war veterans. For more information about how Sunnybrook is inventing the future of healthcare please visit us online at www.sunnybrook.ca


  • Kathleen Sandusky
  • Media Advisor, ICES
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  • Laura Bristow
  • Communications Advisor, Sunnybrook Health Sciences Centre
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  • 416-480-4040


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