The overarching goal of this proposal is to evaluate the extent to which OSA may be a
common, treatable comorbidity in post-COVID patients suffering from cognitive fog and
whether addressing the sleep apnea may help these patients in resolving this distressing
symptom.

According to the World Health Organization (WHO), "post-COVID-19 condition occurs in
individuals with a history of probable or confirmed SARS-CoV-2 infection, usually 3
months from the onset, with symptoms that last for at least 2 months and cannot be
explained by an alternative diagnosis". It is estimated that up to 20 to 90% of post
COVID patients will have at least one persisting symptom that lasts for more than 4
months. According to the WHO, the most common symptoms include, but are not limited to
shortness of breath (78%), fatigue (78%), and cognitive dysfunction (74%). It has serious
economic consequences as 46% of patients were working on a reduced schedule and 23% left
the workforce. Though the underlying pathology is thought to be a pan-inflammatory
response, the etiology can be multifactorial. OSA is one of the possible etiologies as
its symptoms and underlying inflammatory pathophysiology overlaps with that of post COVID
syndrome.

Obstructive sleep apnea (OSA), a pulmonary disorder in which patients have stopping
breathing episodically at night, is common, occurring in up to 60% of post COVID 19
patients. Patients with preexisting OSA have a 59% and 89% chances of developing post
COVID symptoms in men and women respectively. The intermittent 'stopping breathing'
episodes, sleep fragmentation and intermittent hypoxia in patients with OSA triggers a
persistent, chronic low-grade inflammation within the central nervous system leading to
activation of microglia and astrocytes which in turn leads to synaptic loss, neuronal
necrosis and apoptosis which manifests as cognitive deficits. Interestingly, post COVID
syndrome presents with similar symptoms of difficulty breathing and cognitive fog, and is
associated with a similar but independent, chronic inflammatory process in the central
nervous system, leading to synaptic and neuronal loss and cognitive fog. When patients
with pre-existing OSA have post COVID syndrome, there may be worsening of the cognitive
fog because of synergistic increase in inflammatory responses. Further, treatment of
sleep apnea with CPAP can improve cognitive fog as it could decrease the inflammatory
response in post COVID patients with sleep apnea. Hence, it is important to understand
the relationship between the severity of OSA to the severity of cognitive fog, and if
CPAP treatment can decrease the cognitive fog, thereby improve quality of life in post
COVID patients.

The investigator proposes to conduct a four-week longitudinal, observational pilot study
in a sample of 30 patients with sleep apnea, recruited from the post COVID clinic over a
period of one year. The investigator will evaluate the severity of cognitive fog at
baseline and change in cognitive fog with CPAP treatment from baseline to four weeks of
follow up.