Exploring the Role of Nocturnal Hypoxemia and Sleep Fragmentation in Memory Decline: Insights From Explainable...

Area of Science:

• Neurology
• Sleep Medicine
• Cardiology

Background:

• Sleep-disordered breathing (SDB) is associated with cognitive decline, particularly memory impairment.
• The precise mechanisms linking sleep fragmentation, nocturnal hypoxemia, and cognitive deficits remain incompletely understood.

Purpose of the Study:

• To investigate the relationship between micro-arousal burden, oxygen desaturation patterns, and memory decline in patients with moderate-to-severe obstructive sleep apnea (OSA).

Main Methods:

• Retrospective analysis of polysomnographic (PSG) and clinical data from 884 adult patients suspected of SDB.
• Memory decline assessed using the Subjective Cognitive Decline (SCD) instrument.
• Machine learning models used to identify predictors of memory decline from sleep architecture, micro-arousal burdens, and oxygen desaturation metrics.

Main Results:

• The memory decline group was older and had higher rates of hypertension and diabetes.
• Despite similar apnea-hypopnea index (AHI) and arousal index, the memory decline group showed a hypopnea-predominant phenotype with prolonged periods of SpO2 < 95%.
• Machine learning identified spontaneous NREM micro-arousals, REM micro-arousals, and obstructive desaturation metrics as significant predictors of memory decline.

Conclusions:

• The morphological characteristics of oxygen desaturation, rather than absolute event counts, are more strongly associated with memory decline in SDB.
• A hypopnea-dominant SDB phenotype with mild, persistent hypoxia may underlie cognitive decline.
• Hypoxic burden should be prioritized in identifying SDB phenotypes and guiding memory decline treatment.