A recent study led by researchers at the Krembil Brain Institute suggests that short sleep duration may contribute to the development of persistent symptoms of COVID-19, particularly in people with pre-existing medical conditions.
Most people recover fully from COVID-19, but a significant percentage experience lasting symptoms, such as difficulty breathing, fatigue, sleep problems and brain fog. The persistence of these symptoms for more than two months after a person recovers from the acute illness is called post-COVID condition or long COVID.
“Despite nearly 40% of patients going on to experience long COVID, there are still a lot of unknowns about the condition, including what makes one person more susceptible than another,” says Dr. Frances Chung, a Clinician Investigator at the Krembil Brain Institute and ResMed Chair in Anesthesia, Sleep and Perioperative Medicine Research at UHN.
Preliminary evidence suggests that pre-existing medical conditions, including chronic obstructive pulmonary disease (COPD), heart disease and diabetes, increase one’s risk of developing long COVID.
This evidence, together with the known importance of sleep for immune system function, led Dr. Chung to explore whether the odds of developing long COVID are higher among people who have chronic health conditions and whether the impact of these conditions is influenced by sleep duration.
Using an online survey, Dr. Chung’s team collected data from 13,461 adult men and women in 16 countries, 2,508 of whom reported having COVID-19. Of the 1,505 people who reported experiencing long COVID, 945 had at least one chronic medical condition before the pandemic.
The team found that, among people with pre-existing conditions, average sleepers (those who regularly slept for six to nine hours per night) had a 1.8-fold higher risk of developing long COVID; while habitual short sleepers (those who regularly slept for less than six hours per night) had a 3-fold higher risk compared to healthy average sleepers.
Interestingly, despite having similar pre-existing conditions, habitual long sleepers (those who regularly slept for more than nine hours per night) did not have an increased risk of long COVID.
"Our findings suggest that not getting enough sleep may increase susceptibility to long COVID among people with pre-existing health conditions," explains Dr. Linor Berezin, an anesthesiology resident at the University of Toronto and the first author of the study. “This could be due to the detrimental effects of sleep loss on immune responses, such as impaired immunity against pathogens and increased release of inflammatory molecules.”
“Although the proportions of people with pre-existing conditions were generally similar among short, average and long sleepers, we saw that heart conditions were most common among short sleepers,” cautions Dr. Berezin. More research is needed to determine whether the higher prevalence of this condition among short sleepers underpins the team’s observations.
Nonetheless, these findings have important implications for preventing long COVID. "Insufficient sleep is a risk factor that we can change,” says Dr. Chung. “Encouraging at-risk individuals to regularly get a sufficient amount—ideally seven to nine hours— of nighttime sleep is an easy, cost-effective approach to reducing the prevalence of long COVID."
This work was supported by the Ontario Ministry of Health Innovation, the ResMed Foundation, the Wellcome Trust, the National Institute for Health and Care Research, and UHN Foundation.
Berezin L, Waseem R, Merikanto I, Benedict C, Holzinger B, De Gennaro L, Wing YK, Bjorvatn B, Korman M, Morin CM, Espie C, Landtblom AM, Penzel T, Matsui K, Hrubos-Strøm H, Mota-Rolim S, Nadorff MR, Plazzi G, Reis C, Chan RNY, Cunha AS, Yordanova J, Bjelajac AK, Inoue Y, Dauvilliers Y, Partinen M, Chung F. Habitual short sleepers with pre-existing medical conditions are at higher risk of Long COVID. J Clin Sleep Med. 2023 Oct 3. doi: 10.5664/jcsm.10818
Symptoms of long COVID include fatigue, persistent cough, muscle aches and cognitive dysfunction, among others. Getting an optimal amount of good-quality sleep may reduce one’s risk of developing the condition.