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.