Image of person sleeping with moons above
This study used the STOP questionnaire to assess the risk of sleep apnea. The questionnaire comprises four simple questions relating to snoring, tiredness, observed apnea and blood pressure. (Photo: iStock)

A recent study from UHN revealed that individuals at high risk for obstructive sleep apnea are more likely to be diagnosed with COVID-19 and are twice as likely to be hospitalized or treated in intensive care.

Approximately one in 10 adults have obstructive sleep apnea. However, 85 per cent to 90 per cent of those individuals are not aware they have the disease and are not diagnosed. Those with the condition experience broken sleep and interrupted breathing during sleep, which can lead to low blood oxygen levels.

"Our approach was unique in that we were able to explore the effect of undiagnosed sleep apnea on COVID-19 severity in a large and diverse group of individuals in the general population," says Dr. Frances Chung, the senior author of the study and a Clinician Investigator at the Krembil Brain Institute.

A group of more than 20,000 individuals from 14 different countries participated in the study. Participants completed a series of established questionnaires to assess the quality of their sleep, their risk for obstructive sleep apnea, and to assess levels of anxiety and depression.

In addition to providing insights into potential link between obstructive sleep apnea and COVID-19, the results of the study indicated that:

  • Males were three times more likely than females to be hospitalized for COVID-19
  • Individuals with diabetes were three times more likely to be hospitalized for COVID-19
  • Participants who reported experiencing depression were nearly twice as likely as those without depression to be hospitalized for COVID-19

While the findings are in line with previous studies, a few of the results contradicted existing literature.

"Surprisingly, we did not observe a link between physician-diagnosed obstructive sleep apnea and worse COVID-19 outcomes," says Dr. Chung. "This finding may be explained by the fact that those who are aware of their condition are likely managing it with effective treatments, such as continuous positive airway pressure therapy.

"We also failed to observe statistically relevant links between certain established risk factors for COVID-19 severity, such as hypertension or chronic inflammatory lung disease. This is likely because the participants in our study were younger and had fewer chronic health conditions than participants in previous studies."

Frances Chung
Dr. Frances Chung is the lead author of the study and a Clinician Investigator at the Krembil Brain Institute. (Photo: UHN StRIDe Team)

Taken together, the results of this study highlight the importance of screening individuals with COVID-19 for obstructive sleep apnea to help healthcare professionals determine which COVID-19 patients are at risk for developing severe symptoms.

How you can help advance COVID-19 research

With the success of the first worldwide study, Dr. Chung's team is looking for participants to complete a second survey on the effects of long lasting COVID-19 symptoms (Long COVID).

The survey is open to everyone aged 18 years and older – regardless of whether they have experienced COVID-19 symptoms. The time it will take to complete the survey depends on whether participants have experienced symptoms:

  • For those who have not had COVID-19, the survey will take up to 20 minutes
  • For those who have had COVID-19 in the past year, it will take 50 minutes

Participation in the study is voluntary and completely anonymous (no identifiable information is gathered). Those interested in participating, please click for more information.

If you have any questions about participation in this research study, please contact the Principal Investigator, Dr. Frances Chung, UHN, University of Toronto, at 416 670-4253 or

Dr. Chung holds the ResMed Research Chair of Anesthesia, Sleep and Perioperative Medicine at UHN. Morin CM holds a Tier 1 Canada Research Chair in Sleeping Disorders at Université Laval.

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