REM sleep apnea severity is associated with worse verbal memory

A team of researchers led by the University of California, Irvine has found a link between the frequency of rapid eye movement (REM) sleep apnea events and the degree of verbal memory impairment in older adults at risk for Alzheimer's disease. Verbal memory refers to the cognitive ability to store and recall information presented in the form of spoken words or written text, and is particularly vulnerable to Alzheimer's disease.

The study, recently published in the journal Alzheimer's Research & Therapy, found a specific correlation between the severity of sleep apnea—when breathing is interrupted during sleep—and cognitive decline. Higher performance during the REM phase compared to non-REM phases was associated with poorer memory.

“Our results reveal specific memory-related features of sleep apnea, which is important because clinically, events that occur during REM sleep are often ignored or minimized "said study co-author Bryce Mander, assistant professor of psychiatry and human behavior at UC Irvine.

“Most hours of sleep are spent in non-REM sleep, so overall average apnea severity scores may appear much lower than what is typically observed during REM sleep. This means that someone at risk may be misdiagnosed and underdiagnosed because current assessment standards do not focus on the severity of sleep apnea."

“Furthermore,” said study co-author Ruth Benca, professor and chair of the department of psychiatry and behavioral medicine at Wake Forest University School of Medicine, “we found that women tend to have a higher proportion of REM apnea compared with men, which could potentially put them at greater risk of developing Alzheimer's disease."

Scatter plots showing the relationship between (A) apnea-hypopnea index (AHI), (B) respiratory distress index (RDI), and (C) oxygen desaturation index (ODI) during REM sleep and overall learning scores RAVLT score taking into account age, sex, time between assessments, years of education, body mass index (BMI) and APOE4 status. Source: Alzheimer's Research & Therapy (2024). DOI: 10.1186/s13195-024-01446-3

The study included 81 middle-aged and older adults from the Wisconsin Alzheimer's Research Center with elevated risk factors, 62% of whom were women. Participants underwent polysomnography—a comprehensive test that records brain waves, eye movements, muscle activity, blood oxygen levels, heart rate and breathing during sleep—and assessments of verbal memory. The results showed that REM apnea events are a critical factor contributing to verbal memory decline, especially among people with a genetic predisposition to Alzheimer's disease and those with a family history of the disease.

“Our findings highlight the complex relationships between sleep apnea, memory function and Alzheimer's disease risk,” Mander said. “Identifying and addressing REM-specific events is essential to developing proactive, personalized assessment and treatment approaches that are tailored to individual sleep patterns.”