A new study has established a connection between obstructive sleep apnea (OSA) and damage to critical brain areas involved in memory. The research, published on May 7, 2025, in Neurology®, the medical journal of the American Academy of Neurology, suggests that lower oxygen levels during sleep due to OSA may lead to degeneration of brain regions responsible for memory. The study emphasizes that this is an association, not a direct cause-and-effect relationship.
Obstructive sleep apnea is a common sleep disorder where the muscles in the throat relax excessively during sleep, temporarily blocking the airway. This disruption causes individuals to wake up repeatedly to breathe, leading to significant drops in oxygen levels. Over time, these drops can have harmful effects on various bodily systems, including the brain.
A key phase of sleep affected by OSA is REM sleep (Rapid Eye Movement), during which critical functions such as memory consolidation and emotional processing occur. The study, led by Bryce A. Mander, PhD, from the University of California Irvine, found that reduced oxygen levels during REM sleep were strongly associated with damage to small blood vessels in the brain, leading to cognitive decline.
The study involved 37 participants with an average age of 73, none of whom had cognitive impairments or were on sleep medications. Researchers used overnight sleep studies to measure oxygen levels during different sleep stages, including REM sleep, and conducted brain scans to assess brain structure.
Among the 37 participants, 24 had obstructive sleep apnea. Researchers found that lower oxygen levels during REM sleep were strongly associated with higher levels of white matter hyperintensities on brain scans. White matter hyperintensities are bright spots seen on MRI scans that indicate damage to the brain’s white matter, often caused by injury to small blood vessels.
The study revealed a correlation between low blood oxygen levels and the presence of white matter hyperintensities. Specifically, the minimum oxygen saturation levels during sleep and the total time spent with oxygen levels below 90% were predictive of the extent of white matter damage in the brain. A blood oxygen level below 90% is a concerning threshold that can have serious health implications.
Additionally, researchers measured the hippocampus and entorhinal cortex, two brain regions crucial for memory processing. They discovered that higher levels of white matter hyperintensities were linked to reduced hippocampal volume and thinner entorhinal cortex areas. These changes in brain structure could help explain the memory deficits observed in individuals with obstructive sleep apnea.
Participants in the study were also given a memory test before and after sleep to assess sleep-dependent memory. The results indicated that participants with reduced thickness in the entorhinal cortex exhibited greater deficits in memory consolidation during sleep. This finding supports the idea that OSA may contribute to cognitive decline, particularly in aging individuals, by impairing the brain’s ability to consolidate memories.
Dr. Mander explained, “Taken together, our findings may partially explain how obstructive sleep apnea contributes to cognitive decline associated with aging and Alzheimer’s disease through the degeneration of brain regions that support memory consolidation during sleep.” This suggests that OSA may accelerate cognitive decline, particularly in individuals at risk for dementia.
While the study presents significant findings, there are some limitations. The participants were primarily white and Asian, which means the results may not be universally applicable to all populations. Further research is needed to explore whether these findings hold true across different demographic groups.
The study highlights the potential long-term impact of obstructive sleep apnea on cognitive health, particularly memory. It underscores the importance of diagnosing and treating OSA early to prevent or minimize brain damage. Future research could explore how interventions such as continuous positive airway pressure (CPAP) therapy might mitigate the harmful effects of OSA on brain health.
The research was funded by the National Institute on Aging and the American Academy of Sleep Medicine Foundation and provides a crucial step forward in understanding how sleep disorders like OSA can influence brain structure and function, with implications for cognitive aging and Alzheimer’s disease.
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