The question of sleep apnea as the risk factor for COVID-19 arose in a study conducted by the Turku University Hospital and the University of Turku on patients of the first wave of the pandemic.
This is the first COVID-19-related study where sleep apnea as suspected risk factor emerges as the main finding.
The study focused on the register information of COVID-19 patients who were admitted to Turku University Hospital during the first wave of the pandemic in the spring 2020. Southwest Finland, with a population of 480,000, managed the first wave of the pandemic with a relatively small number of infected people.
Patients with a positive test result amounted to 278 individuals. From the infected patients, 28 were admitted to hospital care at Turku University Hospital by 3 May 2020.
The register information of these patients was studied with the aim to unravel the risks for the severe form of COVID-19 and the need for intensive care.
The idea behind the study was the need for real time information about covid-19. The research permission was extensive, because little was known about the novel coronavirus. We quickly observed that there was quite a few cases of sleep apnea among the patients."
Thijs Feuth, MD, Study First Author and Fellow in Pulmonary Diseases, University of Turku
The comparison of the register information revealed that 29 percent of the patients admitted to hospital care had already been diagnosed with sleep apnea. The number is significant, as only 3.1 percent of the population of Southwest Finland is getting treatment for sleep apnea.
Even though the total number of patients in the study was low, the share of sleep apnea patients was high. The extent of sleep apnea among the patients cannot only be explained by the obesity often met in sleep apnea patients, being one of the already known risk factors for severe COVID-19.
"The finding was strong enough to justify the question of sleep apnea as a risk factor for COVID-19. In principle, a patient may need hospital care when they have a COVID-19 infection if they also have sleep apnea. Sleep apnea anticipates a severe form of COVID-19," estimates Feuth in the light of the research findings.
Sleep apnea causes breaks in breathing (apnea) while a person is asleep. The disease is diagnosed by a nocturnal polysomnography.
The connection between sleep apnea and COVID-19 has been confirmed by other studies which are now under review but are already available as pre-publications.
The findings of this new study were comparable with other reported findings. Other findings included higher levels of C-reactive protein (CRP) in those patients that were eventually admitted to intensive care. Most viral diseases do not elevate the CRP levels that much.
Patient information was collected from COVID-19 patients in different wards at Turku University Hospital and several experts participated in the study.
The principal investigator was Chief Physician and Professor of Internal Medicine at the University of Turku Jarmo Oksi from the Department of Infectious Diseases at Turku University Hospital.
The coordinating director of the Sleep and Breathing Centre at Turku University Hospital, Docent Tarja Saaresranta also participated in the study.
Feuth, T., et al. (2020) Is sleep apnea a risk factor for Covid-19? findings from a retrospective cohort study. Sleep Medicine and Disorders International Journal. doi.org/10.15406/smdij.2020.04.00075.