Distinct EEG spectral and functional connectivity patterns in obstructive sleep apnea patients with excessive daytime sleepiness.

Purpose: The study investigated the differences in sleep electroencephalography characteristics between obstructive sleep apnea (OSA) patients with and without excessive daytime sleepiness (EDS), aiming to explore mechanisms underlying the development of EDS in OSA.

Methods: Sixty-one adult OSA patients were divided into OSA + EDS and OSA - EDS groups based on the Epworth Sleepiness Scale (ESS). Electroencephalography (EEG) data were analyzed for power spectral density (PSD) and functional connectivity using coherence and weighted phase lag index (wPLI).

Results: Compared to the OSA - EDS group, the OSA + EDS group exhibited: (1) More severe nocturnal hypoxia during non-rapid eye movement (NREM) sleep; (2) Increased gamma band PSD during NREM stages 1-2; (3) Enhanced wPLI in the delta band during NREM stage 1 and wakefulness, correlated positively with the severity of OSA.

Conclusions: OSA patients with EDS show distinct neurophysiological patterns characterized by gamma hyperactivation during light sleep and compensatory delta-band synchronization during sleep-wake transition phase. Respiratory events may disrupt EEG dynamics in specific frequency bands, contributing to sleep instability and EDS. These findings highlight the importance of NREM sleep disruption and support tailored therapeutic interventions targeting cortical instability in OSA patients with persistent EDS.