EEG spectral analysis of nighttime sleep and daytime MSLTs and neurocognitive evaluations in obstructive sleep apnea patients with residual sleepiness.

STUDY OBJECTIVES: To explore neurophysiological and neurocognitive characteristics of OSA patients with residual excessive sleepiness (RES) using EEG spectral analysis and multidimensional cognitive assessments. METHODS: This case-control study included 76 participants (38 RES, 38 Non-RES) from our RES cohort. Polysomnography (PSG) and multiple sleep latency tests (MSLTs) were recorded and used to obtain relative EEG spectral power. A series of standard neurocognitive assessments were conducted during the first MSLT interval (approximately 09:00-11:00 AM). RESULTS: In PSG and MSLTs, RES patients showed increased delta and theta power and decreased alpha and beta power (all FDR-adjusted q<0.05). RES patients demonstrated multidimensional cognitive impairments, including longer WCST reaction time (mean difference [MD] = -642.71 ms, 95% CI: -1045.70 to -239.72, p = 0.002, partial η2 = 0.130), longer SCWT color-word reaction time (MD = -16.02 s, 95% CI: -25.32 to -6.71, p = 0.001, partial η2 = 0.148), and more PVT lapses (MD = -3.65, 95% CI: -5.28 to -2.03, p < 0.001, partial η2 = 0.228). The EEG spectral patterns of increased delta-theta power and decreased alpha-beta power were significantly associated with impairments in executive function, processing speed, working memory and selective attention, while the decreased alpha-beta power was more related to impairment of vigilance and sustained attention. CONCLUSIONS: RES patients exhibit a characteristic EEG power spectrum marked by increased delta-theta and decreased alpha-beta power values, indicating sleep-wake dysregulation. RES patients also demonstrate multidimensional cognitive impairments, including deficits in processing speed, working memory, attention, and executive function, with distinct neurophysiological correlates.