Glossopharyngeal airway narrowing is the leading factor of REM-related oxygen desaturation in patients with moderate or severe OSA by the prolongation of apnea events during REM sleep.
Key Findings
Results
REM-related oxygen desaturation group had significantly more severe lowest overnight oxygen saturation compared to the NREM-related OD group.
Lowest oxygen saturation overnight was 56.14 ± 7.06% in the REM-related OD group vs. 70.92 ± 14.49% in the NREM-related OD group (p = 0.009).
33 male OSA patients with AHI > 15 events/h were divided into REM-related OD group (n = 15) and NREM-related OD group (n = 18).
REM-related OD was defined as REM-OD/NREM-OD ratio ≥ 1.5.
Mean AHI was 68.01 ± 18.35 events/h in the REM-related OD group and 57.48 ± 28.81 events/h in the NREM-related OD group.
Results
The REM-related OD group had a significantly narrower glossopharyngeal airway as measured by 3D-CT.
Minimal anteroposterior airway dimension was smaller in the REM-related OD group (12.41 ± 2.99 vs. 17.58 ± 4.78 mm, p = 0.020).
Minimal cross-sectional airway area was smaller in the REM-related OD group (119.81 ± 30.94 vs. 199.78 ± 75.02 mm², p = 0.005).
Upper airway anatomy was measured using three-dimensional computed tomography (3D-CT) in all subjects.
The glossopharyngeal region specifically, not other airway segments, showed significant differences between groups.
Results
Genioglossus electromyography (GGEMG) variables were similar between the two groups, except for apnea duration during REM sleep.
Apnea time during the REM period was significantly longer in the REM-related OD group (p < 0.001).
GGEMG was recorded using intraoral surface electrodes during overnight polysomnography.
The similarity of most GGEMG variables between groups suggests that genioglossus muscle activity differences do not primarily explain REM-related OD.
The prolongation of apnea events during REM sleep was identified as the mechanism linking glossopharyngeal narrowing to greater oxygen desaturation.
Methods
The study used a pilot design with overnight polysomnography combined with synchronous genioglossus electromyography and 3D-CT upper airway measurement.
All 33 subjects were male OSA patients with moderate or severe OSA (AHI > 15 events/h).
Both REM-OD and NREM-OD were calculated as average oxygen desaturation during respective sleep stages.
3D-CT was performed on all subjects to measure upper airway anatomy.
Independent t-tests were used to analyze differences between the two groups.
The study is described as a pilot study, indicating a relatively small sample size and exploratory nature.
What This Means
This research suggests that in patients with moderate to severe obstructive sleep apnea (OSA), the main reason some people experience worse drops in blood oxygen levels specifically during REM (dream) sleep compared to other sleep stages is the physical narrowing of a specific part of the throat called the glossopharyngeal airway. Using CT scans, researchers found that patients whose oxygen levels dropped more during REM sleep had a measurably narrower airway in this region — both in terms of front-to-back distance and cross-sectional area — compared to patients whose oxygen drops were more evenly distributed across sleep stages. This narrower airway appeared to cause breathing pauses to last longer during REM sleep, which in turn caused more severe drops in oxygen levels.
Interestingly, the study found that the tongue muscle (genioglossus) activity was similar between both groups during most of sleep, suggesting that muscle function differences are not the primary explanation for why some OSA patients have worse oxygen drops during REM sleep. The most severe overnight oxygen levels recorded were significantly lower in the REM-related group (around 56% vs. 71% in the other group), highlighting that this subgroup of OSA patients may face greater health risks.
This research suggests that identifying the specific location of airway collapse — particularly in the glossopharyngeal region — could be important for understanding and potentially treating REM-related oxygen desaturation in OSA patients. Since this was a small pilot study involving only 33 male patients, larger studies are needed to confirm these findings and explore whether targeted treatments for glossopharyngeal narrowing could benefit this patient group.
Zhou Y, Yin G, Xu J, Cao X, Ye J. (2026). Glossopharyngeal airway collapse is the main factor leading REM-related oxygen desaturation in patients with obstructive sleep apnea: a pilot study.. Sleep & breathing = Schlaf & Atmung. https://doi.org/10.1007/s11325-025-03523-9