Evening-to-morning changes in respiratory muscle strength reflect acute overnight respiratory muscle loading in patients with OSA and provide physiological insight into short-term neuromuscular adaptations associated with recurrent apnea-hypopnea events.
Key Findings
Results
Positive changes in maximal inspiratory pressure (ΔMIP) from evening to morning were significantly higher in OSA patients compared to controls.
80 patients undergoing overnight polysomnography for suspected OSA were prospectively evaluated between February and June 2025
ΔMIP was calculated as morning minus evening MIP values
Positive ΔMIP values were significantly higher in OSA patients versus controls (p < 0.001)
Changes were interpreted as reflecting acute overnight respiratory muscle loading
Results
Positive changes in maximal expiratory pressure (ΔMEP) from evening to morning were significantly higher in OSA patients compared to controls.
ΔMEP was calculated as morning minus evening MEP values
Positive ΔMEP values were significantly higher in OSA patients versus controls (p < 0.001)
Both MIP and MEP were measured before and after overnight polysomnography
The increases in both ΔMIP and ΔMEP suggest neuromuscular adaptation to recurrent apnea-hypopnea events
Results
Both minimum and maximum oxygen saturation values during sleep were significantly lower in the OSA group than in controls.
Minimum oxygen saturation was significantly lower in the OSA group compared to controls (p < 0.001)
Maximum oxygen saturation was also significantly lower in the OSA group compared to controls (p = 0.009)
Lower oxygen saturation values reflect the intermittent hypoxemia characteristic of OSA
Results
ΔMIP was independently and positively associated with BMI, REM-AHI, and supine AHI, and negatively associated with oxygen desaturation index (ODI) in multivariate regression analysis.
BMI was positively associated with ΔMIP (β = 0.609, p < 0.001)
REM-AHI was positively associated with ΔMIP (β = 0.693, p < 0.001)
Supine AHI was positively associated with ΔMIP (β = 1.597, p < 0.001)
ODI was negatively associated with ΔMIP (β = -1.000, p < 0.001)
Results
ΔMEP was independently and positively associated with BMI, REM-AHI, and supine AHI, and negatively associated with ODI in multivariate regression analysis.
BMI was positively associated with ΔMEP (β = 0.370, p = 0.001)
REM-AHI was positively associated with ΔMEP (β = 0.506, p = 0.002)
Supine AHI was positively associated with ΔMEP (β = 1.706, p < 0.001)
ODI was negatively associated with ΔMEP (β = -1.128, p < 0.001)
Methods
The study design involved prospective measurement of maximal inspiratory and expiratory pressures in the evening before and morning after overnight polysomnography.
Study enrolled 80 patients undergoing overnight polysomnography for suspected OSA
Recruitment occurred between February and June 2025
MIP and MEP were measured at two time points: evening before PSG and morning after PSG
Changes (Δ values) were defined as morning minus evening measurements
What This Means
This research suggests that in patients with obstructive sleep apnea (OSA), the breathing muscles measurably change in strength overnight. The researchers measured how hard patients could breathe in and out (called maximal inspiratory and expiratory pressure) both before going to sleep and again after waking up from a sleep study. They found that OSA patients showed greater increases in these muscle strength measures overnight compared to people without OSA, suggesting that the repeated effort of breathing against a blocked airway during sleep causes a short-term strengthening or adaptation response in the respiratory muscles.
The study also found that the degree of overnight change in breathing muscle strength was linked to specific features of the sleep apnea itself — particularly how severe the apneas were during REM sleep and while lying on the back, as well as the patient's body mass index. Interestingly, greater oxygen desaturation over the night was actually associated with smaller increases in muscle strength, which may suggest that when oxygen levels drop frequently, the muscles respond differently than when the airway is mechanically obstructed without as much oxygen loss.
This research matters because it provides a simple, non-invasive way to capture information about what the breathing muscles experience overnight during sleep apnea. The evening-to-morning changes in respiratory muscle strength could potentially serve as a physiological marker of overnight respiratory loading, offering new insight into how the body adapts — or struggles to adapt — to the repeated muscle effort demanded by OSA throughout the night.
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Kerget B, Çınar &, Çelik K, Özkan H, Aksakal A, Uçar E. (2026). Short-term changes in respiratory muscle strength before and after sleep in patients with obstructive sleep apnea.. Sleep & breathing = Schlaf & Atmung. https://doi.org/10.1007/s11325-026-03708-w