New Study Links Sleep Apnea to Changes in Brain Areas Supporting Memory
A new peer-reviewed study published in Neurology explores how obstructive sleep apnea—a sleep disorder that lowers blood oxygen during the night—may be connected to changes in brain regions responsible for memory. Using brain imaging and cognitive tests, researchers analyzed how oxygen saturation during rapid eye movement (REM) sleep relates to small vessel brain damage and memory function in older adults. The study, led by scientists at the University of California, Irvine, does not show causation but adds detail to the growing understanding of how sleep disorders may impact brain health in aging.
Note: This article is intended for general information and educational purposes. It summarizes scientific research in accessible language for a broad audience and is not an official scientific press release.
Study Explores the Connection Between Sleep Apnea and Memory
The study, led by neuroscientist Bryce A. Mander, PhD, at the UCI Center for the Neurobiology of Learning and Memory, was published on May 7, 2025, in Neurology. The authors set out to determine whether reduced oxygen saturation during REM sleep is associated with damage to small blood vessels in the brain and with structural changes in areas critical for memory.
Participants and Research Methods
Researchers enrolled 37 older adults with an average age of 73, all without diagnosed cognitive impairment and none taking sleep medications. Among the participants, 24 had obstructive sleep apnea (OSA), while 13 did not. Each individual completed an overnight sleep study to monitor oxygen levels during all stages of sleep, with a specific focus on REM sleep—the phase when most dreaming occurs and which is important for memory consolidation.
In addition to the sleep studies, participants underwent high-resolution brain imaging (MRI) to assess structural features such as white matter hyperintensities. These are bright spots that appear on MRI scans and are considered markers of small vessel damage in the brain. The researchers also measured the volume of the hippocampus and the thickness of the entorhinal cortex, both brain regions known to play key roles in memory.
To evaluate the relationship between sleep and memory, participants took cognitive tests before and after sleep to measure sleep-dependent memory performance. These tests were designed to reveal whether changes in sleep quality and oxygen levels might be reflected in a person’s ability to remember information learned the previous day.
What Makes This Study Distinctive
According to the study and as reported by Neuroscience News, the researchers found that lower oxygen saturation during REM sleep was associated with a greater number of white matter hyperintensities in the brain. These changes are thought to indicate damage to small blood vessels. The study also found that the amount of white matter hyperintensities was linked to decreased volume in the hippocampus and thinning of the entorhinal cortex—two regions essential for forming and retrieving memories.
The researchers further observed that the extent of these structural brain changes was related to the minimum blood oxygen saturation during sleep as well as the total time spent below 90% oxygen saturation. According to the article, having a blood oxygen level of 90% or lower is considered a cause for concern. The findings suggest that even relatively short periods of low oxygen during REM sleep may be associated with measurable changes in brain structure.
Key Findings from the Authors
Participants who exhibited greater evidence of small vessel brain damage and reduced memory region structure also performed less well on sleep-dependent memory tests. In other words, lower oxygen levels during REM sleep and the resulting structural changes in the brain were associated with poorer memory performance after sleep. According to Neuroscience News, “deficits in sleep-dependent memory were linked to reduced thickness of the entorhinal cortex.”
Study author Bryce A. Mander, PhD, commented in an official news release from the American Academy of Neurology: “Obstructive sleep apnea is a sleep disorder that increases with age, and low oxygen levels during sleep can harm the ability of our brain and body to function properly. Our study found that low oxygen levels from obstructive sleep apnea, especially during REM sleep, may be linked to cognitive decline due to damage to the small blood vessels in the brain and the downstream impact of this damage on parts of the brain associated with memory.”
Importantly, the authors emphasize that the study does not prove a cause-and-effect relationship between obstructive sleep apnea and brain changes. As stated in both the original research and the Neuroscience News summary, the results “show an association” but do not establish that sleep apnea causes degeneration in memory-related brain regions. The researchers note that further investigation is needed to clarify the clinical significance and long-term implications of these findings.
Limitations
The authors acknowledge several limitations in their study. Most participants were White or Asian, which means the results may not be fully generalizable to other populations. The sample size was relatively small, and the observational nature of the research means that causality cannot be established.
Conclusion
In summary, the authors report that obstructive sleep apnea, particularly when it results in lower oxygen levels during REM sleep, is associated with small vessel brain damage and changes in memory-related brain regions in older adults. These brain changes are also linked to poorer performance on memory tasks following sleep. While the findings contribute to the understanding of how sleep disorders and cognitive changes may be connected in aging, additional research is necessary to explore potential mechanisms and outcomes.
DOI: https://doi.org/10.1212/WNL.0000000000213639
The information in this article is provided for informational purposes only and is not medical advice. For medical advice, please consult your doctor.
