Facility-measured nocturnal hypoxemia and sleep among adults with long COVID versus age- and sex-matched healthy adults: a preliminary observational study.

Study objectives: Persistent post-acute sequelae of SARS-CoV-2 infection, i.e. long COVID, impacts multiple organ systems. While lower blood oxygen is expected when SARS-CoV-2 infects the lungs, hypoxia without pulmonary symptoms may continue after the acute phase. Ventilation and blood oxygen are more vulnerable during sleep, but nocturnal hypoxemia hasn't been studied in people with long COVID in a facility setting using gold-standard polysomnography (PSG).

Methods: We conducted an observational study with 50 participants (25 long COVID, 25 age-sex-matched healthy controls) using in-laboratory overnight PSG. We calculated the average SpO₂, average SpO₂ after removing desaturations, the respiratory rate in different sleep periods, and the hypoxic costs using all desaturations.

Results: We found that average SpO₂ was lower in participants with long COVID: 1.0% lower after sleep onset (p = .004) and 0.7% lower during REM (p = .002); average SpO₂ after removing desaturations was also lower in participants with long COVID: 1.3% lower after sleep onset (p = .002), 0.9% lower during REM (p = .0004), and 1.4% lower during NREM (p = .003); and respiratory rate was 1.4/minute higher in participants with long COVID during REM (p = .005). There were no significant differences in SpO₂ and respiratory rate before sleep onset, the within-participant change from before to after sleep onset, or hypoxic costs.

Conclusions: The results suggest that long COVID had a persistent lower nocturnal blood oxygen saturation, and support the need for a large-scale study of nocturnal hypoxemia in people with long COVID compared to the general population.