Identify the relationship of obstructive sleep apnea (OSA) prevalence with post-COVID-19 fatigue that remains at least six months after acute disease

The presence of fatigue symptoms up to 6-7 months after acute COVID-19 disease, similar to myalgic encephalomyelitis/chronic fatigue syndrome, also observed after other viral infections, have been reported as the most frequent post-COVID-19 symptom (Townsend et al., 2020).

There is a physiological plausibility for OSA being a causal factor to COVID-19 morbidity and fatigue symptoms by nocturnal hypoxemia, exacerbating or causing endothelial dysfunction, inflammation, oxidative stress, microaspiration and cardiac dysfunction. OSA activates the renin-angiotensin-aldosterone system (RAAS) and angiotensin-converting enzyme-2 (ACE2), which is the SARS-CoV-2 entry receptor in the cells (Miller et al., 2021).

In this study we will identify the prevalence of OSA and it's relation with post-COVID-19 fatigue that remains for at least six month after the acute disease, in patients that attend the post-COVID-19 Out Patients Hospital Clinics. It will be studied also the relation between fatigue and vaccination status, nocturnal hypoxemia, day time sleepness and the acute COVID-19 severity.

Data collection will be performed by a questionnaire administered by qualified clinical study staff (i.e., by physicians who conduct the post-COVID-19 medical consultation).

Demographic, clinical data and clinical research forms will be collected between 6-7th month after the diagnosis of COVID-19 (t1) and 9 months later (t2).

Fatigue will be assessed using the Chalder fatigue scale - CFQ-11 (Chalter et al., 1993).

The evaluation of OSA related daytime sleepiness will be measured using the Epworth Sleepiness Scale - ESS (Johns, 1991). The OSA diagnosis will be performed using portable monitoring device type III (in-home polygraphy), between 6-7th month after the diagnosis of COVID-19 (t1).

Inclusion Criteria:

(1) ≥18 years; (2) previous COVID-19 at least six months before the initial study protocol evaluation; (3) persistent symptoms after cure criteria defined by WHO; (4) patients who attend the post-COVID-19 follow-up consultation of the study centers. (5) SARS-CoV-2 infection confirmed by a positive real-time reverse-transcription polymerase chain reaction on a nasopharyngeal swab (6) patients who agree to sign the Written informed consent (following the ethics committee protocol).

Exclusion Criteria:

(1) patients who had a concomitant neurological disorder that could increase OSA risk (such as stroke, Parkinson disease, or amyotrophic lateral sclerosis); (2) patients who were on invasive mechanical ventilation. (3) patients with persistent fatigue symptoms,6 months before SARS-CoV-2 infection (4) patients without SARS-CoV-2 positive real-time reverse-transcription polymerase chain reaction on a nasopharyngeal swab

The study will be conducted in twelve Portuguese Hospitals, Universitary and District, in which a follow-up post-COVID-19 medical consultation has been implemented All patients that attend the follow-up post COVID-19 consultation will be invited to participate in the study.