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A team of researchers from Iceland recently studied the relationship between obstructive sleep apnea (OSA) and severe coronavirus disease 2019 (COVID-19). They tried to establish if confounders played any role, such as several known risk factors for severe COVID-19 associated with OSA.
Publishing their study on the subject in the journal Sleep, the researchers report that OSA is an independent risk factor for severe COVID-19; with OSA, there is a twofold increase in the risk of severe COVID-19.
The ongoing COVID-19 pandemic is caused by severe acute respiratory syndrome coronavirus 2 (SARS-COV-2). Many of the infections are mild and self-limiting. However, few cases, such as one in ten infections, are severe COVID-19, defined as hospitalization or death.
The severe COVID-19 cases are mostly associated with comorbid conditions, including obesity, heart failure, chronic kidney disease (CKD), diabetes mellitus, chronic lung disease, chronic liver disease, and malignancies. Among these, OSA is not sufficiently established if it is a true risk factor for severe COVID-19.
OSA is a sleep disorder where the throat muscles relax, causing the airway to block, leading to breathing issues during sleep. Though underdiagnosed, OSA is one of the most common chronic diseases in Western countries. It is strongly associated with male gender, obesity, diabetes mellitus, and heart failure - all of which are risk factors for severe COVID-19.
Therefore, the present research is undertaken to rule out the confounders that are the comorbidities associated with both OSA and severe COVID-19.
Although OSA is proposed as a risk factor for the severe COVID-19, no significant clinical data reflects the general population. Using the centralized registries data in Iceland, the researchers in the present study investigated the association between OSA and severe COVID-19.
Study Design and Findings
The study cohort included all community-dwelling Icelandic citizens (n=4756; 1.3% of the total population) who were 18 years or older and diagnosed with SARS-CoV-2 infection in 2020. Because all the SARS CoV-2-positive individuals in Iceland were enrolled in a telehealth monitoring service at the COVID-19 Outpatient Clinic of Landspitali – The National University Hospital of Iceland (LUH), a nationwide study cohort was available for the researchers.
Severe COVID-19 is defined as hospitalization and/or death while receiving care at the COVID-19 Outpatient Clinic. The OSA diagnosis in Iceland is conducted at the Division of Respiratory Medicine and Sleep at LUH, also the sole provider of positive airway pressure (PAP) treatment. In addition to evaluating whether OSA is an independent risk factor for severe COVID-19, the researchers also investigated whether the OSA patients undergoing the PAP had a higher risk of severe COVID-19 or if it mitigated the risk.
Using logistic regression models and inverse probability weighting, the researchers calculated the associations between OSA and the severe COVID-19. Of 4,756 individuals diagnosed with SARS-CoV-2 infection, 185 were diagnosed with OSA. Out of 238 severe COVID-19 patients, 38 OSA individuals were associated with poor outcomes.
The researchers reported that the OSA was associated with a two-fold increase in the risk of severe COVID-19. The researchers adjusted the association for demographic characteristics and various comorbidities and found little change, indicating an OSA-associated risk for severe COVID-19 is not explained by obesity or other comorbidities.
The researchers tabulated the previous studies on the association of the OSA and the severe COVID-19, highlighting the study's outcomes, strengths, and limitations. They discussed the link between OSA and severe COVID-19 based on the clinical manifestations of chronic low-grade inflammation, hypoxemia, oxidative stress, hypoxia, and other complications, in OSA patients and SARS-CoV-2 infected individuals.
Analyzing the association between positive airway pressure (PAP) treatment and outcomes of OSA patients with SARS-CoV-2 infection, the researchers reported the study cohort to be relatively small. Hence, it limits the strength of this analysis. While an increased risk for severe COVID-19 among OSA patients treated with PAP, specifically for long-term, was found, the researchers noted that the data was insufficient for conclusive clinical recommendations.
Notably, this study period was prior to infections caused by the SARS-CoV-2 variants (Alpha, Beta, and Delta variants) prevalent in Iceland, and the vaccination program had not been initiated.
The researchers conducted a nationwide study to find the relation between OSA and severe COVID-19; they suggest that OSA is an independent risk factor for severe COVID-19, defined as hospitalization or death. This is an important finding that should be considered during the clinical evaluation of risk profiles for COVID-19.
The researchers recommended larger studies to evaluate the different phenotypes of OSA further, examine possible pathophysiological mechanisms, and investigate the effect of PAP treatment on the outcomes of COVID-19.