Facility-measured nocturnal hypoxemia and sleep among adults with long COVID versus age- and sex-matched healthy adults…, 2025, Sun+

[SNT Gatchaman]

Facility-measured nocturnal hypoxemia and sleep among adults with long COVID versus age- and sex-matched healthy adults: a preliminary observational study
Sun, Haoqi; Dang, Rammy; Haack, Monika; Hauser, Kristine; Scott-Sutherland, Jennifer; Westover, M Brandon; Parthasarathy, Sairam; Redline, Susan; Thomas, Robert J; Mullington, Janet M

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.

Link | PDF (SLEEP Advances) [Open Access]

 

[wigglethemouse]

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.

Forgetting significance, the median difference is 1% lower before sleep, which matches during sleep. The abstract on first read makes this seem like it only occurs during sleep, but it looks like it is also present before sleep. The conclusion perhaps should have suggested a follow up study to check if also present during the day.

 

[Utsikt]

Does the differences matter? Are they within the normal ranges? Can they be caused by confounding factors?

 

[SNT Gatchaman]

The cohort contained 50 participants, including 25 long COVID and 25 age-sex-matched healthy controls. […] Participants were 37–38 years old on average, and 68% female and 32% male. By study design, there were no differences in age and sex.

We found that patients with long COVID compared to healthy controls had a persistent lower nocturnal blood oxygen saturation i.e. the average SpO2 after removing desaturations after sleep onset, especially during REM sleep. This difference emerged as early as 5 to 10 minutes after sleep onset. There was no difference in hypoxic costs, indicating the depth and duration of episodic desaturations were similar in participants with long-term COVID compared to healthy controls. We also found that the long COVID participants had reduced sleep efficiency, longer sleep latency and REM latency, less REM and N2 sleep, and less N3 in the first half of the night. It is unknown if such sleep architecture changes are related to the gas exchange pattern.

Possible explanations of the subclinical hypoxia include the subtle persistence of lung injury following COVID as supported by reports of shortness of breath in 10 out of 25 of our participants with long COVID, and also many other factors, including endothelial functions. This could include mild levels of ventilation-perfusion mismatch or reduced gas diffusing capacity

The mild reduction in oxygen saturation observed during sleep in people with long COVID may provide a marker of long COVID-related organ dysfunction. As oxygen saturations are easy to track even with consumer wearables or oximeters, tracking this mild hypoxia, even if not directly pathological, may provide prognostic information throughout residual disease or recovery.

while the changes observed are small in magnitude, they suggest that patients with long COVID may experience persistent cardiopulmonary impairment even 1 year after their acute infection.