A study led by UC Irvine links the frequency of sleep apnea events during REM sleep to severe verbal memory impairment in older adults at risk for Alzheimer’s. The research emphasizes the need for specific clinical focus on REM-related apnea events to improve diagnosis and treatment, especially noting differences in sleep apnea patterns between men and women.

New research identifies unique factors in elderly individuals at risk for Alzheimer’s, paving the way for tailored interventions.

A study conducted by a team from the University of California, Irvine has discovered a correlation between the number of sleep apnea episodes during the rapid-eye-movement (REM) sleep stage and the degree of verbal memory decline in older adults who are at risk for Alzheimer’s disease. Verbal memory is the mental capacity to remember and recollect information conveyed verbally or in writing, and it is especially susceptible to deterioration in Alzheimer’s.

The study, recently published online in the journal Alzheimer’s Research & Therapy, discovered a specific correlation between the severity of sleep apnea – when breathing pauses while an individual is sleeping – and diminished cognition. Higher ratios during REM compared to non-REM stages were associated with worse memory performance.

“Our findings identified the specific features of sleep apnea that are associated with memory, which is important because clinically, events occurring during REM sleep are often overlooked or minimized,” said co-corresponding author Bryce Mander, UC Irvine associate professor of psychiatry & human behavior. “Most hours of sleep are non-REM, so the overall averages of apnea severity can look much lower than what is typically observed during REM sleep. This means that someone at risk can be misdiagnosed and undertreated because current evaluation standards are not focused on sleep-stage-specific apnea severity.”

Gender Differences in Sleep Apnea

“Furthermore,” said co-corresponding author Ruth Benca, professor and chair of psychiatry and behavioral medicine at Wake Forest University School of Medicine, “we found that women are more likely to have a greater proportion of their apneic events in REM sleep in comparison to men, which could potentially be contributing to their greater risk for Alzheimer’s disease.”

The study involved 81 middle-aged and older adults from the Wisconsin Alzheimer’s Disease Research Center with heightened risk factors, of whom 62 percent were female. Participants underwent polysomnography – a comprehensive test that records brain waves, eye movements, muscle activity, blood oxygen levels, heart rate, and breathing during sleep – and verbal memory assessments. Results showed apnea events during REM to be a critical factor contributing to verbal memory decline, especially among individuals with a genetic predisposition to Alzheimer’s and those with a parental history of the disease.

“Our findings highlight the intricate relationship among sleep apnea, memory function, and Alzheimer’s risk,” Mander said. “Identifying and addressing REM-specific events are crucial for developing proactive, personalized approaches to assessment and treatment that are tailored to individual sleep patterns.”

Reference: “Older adults at greater risk for Alzheimer’s disease show stronger associations between sleep apnea severity in REM sleep and verbal memory” by Kitty K. Lui, Abhishek Dave, Kate E. Sprecher, Miranda G. Chappel-Farley, Brady A. Riedner, Margo B. Heston, Chase E. Taylor, Cynthia M. Carlsson, Ozioma C. Okonkwo, Sanjay Asthana, Sterling C. Johnson, Barbara B. Bendlin, Bryce A. Mander and Ruth M. Benca, 9 May 2024, Alzheimer’s Research & Therapy.
DOI: 10.1186/s13195-024-01446-3

The team also included lead author Kitty K. Lui, a graduate student in the San Diego State University/University of California, San Diego joint doctoral program in clinical psychology, and faculty and graduate students from UC Irvine, UC San Diego, the Wisconsin Alzheimer’s Disease Research Center and the University of Kentucky.

This work was supported by the National Institute on Aging under grants R56 AG052698, R01 AG027161, R01 AG021155, ADRC P50 AG033514, R01 AG037639 and K01 AG068353; by the National Institutes of Health’s Ruth L. Kirschstein National Research Service Award F31 AG048732; and by the National Center for Advancing Translational Sciences’ Clinical and Translational Science Awards Program under grant UL1TR000427.