Slow-wave sleep, oxygen desaturation, and memory consolidation in sleep-disturbed individuals

Abstract

Slow-wave sleep (SWS) plays a crucial role in memory consolidation, yet its disruption in obstructive sleep apnea (OSA) remains poorly understood. This study investigates the relationship between SWS characteristics, nocturnal oxygen desaturation, and memory performance in individuals with sleep disturbances. This cross-sectional study included 49 participants with memory complaints and sleep disturbances who underwent overnight polysomnography (PSG) and cognitive assessments to determine the presence and severity of OSA. SWS parameters, including the slow-wave index, amplitude, and duration, were extracted from PSG data alongside the apnea-hypopnea index (AHI) and oxygen desaturation index (ODI-3 %). Memory consolidation was assessed pre- and post-sleep using the Word Sequence Learning Test (WSLT), with the WSLT-Memory Index Score (WSLT-MIS) as the primary outcome measure. Multiple linear regression models adjusted for age, BMI, and education were used to analyze associations between sleep parameters and memory outcomes. Higher ODI-3 % and AHI were significantly associated with poorer memory consolidation, as indicated by lower WSLT-MIS scores (p < 0.05). AHI during NREM sleep was more strongly associated with poorer memory consolidation compared to AHI during REM sleep. Conversely, a higher slow-wave index was positively correlated with better WSLT-MIS scores and retention rates (p < 0.05). These findings highlight the critical role of SWS in memory consolidation and the detrimental effects of OSA-related sleep disturbances. While CPAP therapy remains the standard treatment for improving oxygenation and reducing sleep fragmentation in OSA, additional strategies aimed at enhancing SWS may further support cognitive function. Longitudinal studies and neuroimaging approaches are needed to better understand the mechanisms linking SWS enhancement and cognitive health.