Introduction: Obstructive sleep apnea (OSA) is influenced by sleep architecture with rapid eye movement (REM) sleep having the most adverse influence, especially in women. There is little data defining the influence of slow-wave sleep (SWS) on OSA. We wished to study the influence of SWS on OSA and identify differences attributable to gender and/or age, if any.
Methods: Retrospective study of polysomnography (PSG) records of adult patients referred for diagnostic PSG. Records were excluded if they underwent split night or positive airway pressure titration studies, had <180 min of total sleep time (TST) and/or <40% sleep efficiency, or had SWS <5 min and/or <1% of TST. The apnea-hypopnea index (AHI) recorded during SWS was compared with that measured during other non-rapid eye movement (NREM) sleep and during REM sleep. The REM-SWS difference in AHI was measured, and compared between genders.
Results: Records from 239 patients were included. The mean AHI in all subjects was 17.7 ± 22.6. The SWS AHI was 6.8 ± 18.9, compared to the REM AHI of 24.9 ± 25.8, and NREM AHI of 15.8 ± 22.8. Females had significantly higher SWS by percentage, and lower NREM AHI (P < 0.0001) and SWS AHI (P = 0.03). Among patients with OSA (AHI ≥5), the difference between REM AHI and SWS AHI was greater in women than in men (34.2 ± 27.4 vs. 21.6 ± 26.0, P = 0.006).
Conclusions: The upper airway appears to be less susceptible to OSA during SWS than during REM and other NREM sleep. This may be related to phase-specific influences on both dynamic upper airway control as well as loop gain. Gender and age appear to modify this effect.