Link Between REM Sleep Sleep Apnea and Memory-Related Brain Changes

Recent research published in the journal Neurology highlights a significant association between sleep apnea during REM sleep and alterations in brain structures involved in memory. The study underscores how obstructive sleep apnea (OSA), a disorder characterized by repeated episodes of airway obstruction leading to reduced oxygen levels during sleep, may contribute to neural degeneration, particularly in regions critical for memory processing.

Obstructive sleep apnea occurs when the relaxation of throat muscles blocks airflow, causing frequent awakenings to resume breathing. This interruption results in fragmented sleep and lowered oxygen saturation levels, which can adversely affect small blood vessels in the brain. REM sleep, the stage associated with vivid dreams and crucial for memory consolidation and emotional regulation, appears particularly vulnerable.

The study involved 37 older adults, averaging 73 years of age, none of whom had cognitive impairments or were on sleep medications. Participants underwent overnight sleep studies with continuous oxygen monitoring and brain imaging scans. The findings revealed that lower oxygen levels during REM sleep correlate with increased white matter hyperintensities, which are markers of brain tissue damage caused by small vessel injury.

Furthermore, lower oxygen saturation and prolonged periods with oxygen levels below 90% predicted greater white matter damage. These brain changes were linked to reduced volume and thickness in the hippocampus and entorhinal cortex—regions vital for memory functions. Participants also performed memory tests before and after sleep, with results indicating that structural brain changes were associated with impaired sleep-dependent memory consolidation.

Lead researcher Bryce A. Mander, Ph.D., from the University of California Irvine, emphasized that these findings could partially explain how OSA contributes to cognitive decline and Alzheimer’s disease in aging populations. Although causality cannot be confirmed from this study alone, the strong association suggests that managing oxygen levels during sleep might benefit brain health.

Limitations include a predominantly white and Asian participant group, which may limit generalizability. Nevertheless, this research underscores the importance of diagnosing and treating sleep apnea, especially during REM sleep, to potentially prevent or mitigate early brain damage associated with cognitive decline.