• Posted May 8, 2025

Sleep Apnea Linked To Memory-Related Brain Decline

Sleep apnea could be costing you brain power and increasing your risk of dementia and Alzheimer’s disease, a new study says.

The drop in blood oxygen levels that occurs during a sleep apnea episode appears to be linked to degeneration of brain regions associated with memory, researchers reported May 7 in the journal Neurology.

These brain changes were strongly associated with sleep apnea that occurred during rapid eye movement (REM) sleep, the stage of sleep that involves dreaming and consolidation of the day’s new memories, researchers said.

The lower a person’s oxygen levels drop due to sleep apnea during REM sleep, the more severe the degeneration to the brain, results show.

“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,” senior researcher Bryce Mander, an associate professor of psychiatry and human behavior at the University of California-Irvine, said in a news release.

“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,” he said.

People with sleep apnea stop breathing while asleep. The resulting decline in blood oxygen levels causes their brain to jolt them to wakefulness, at least enough for them to resume breathing.

For the study, researchers performed brain scans on and tracked the sleep of 37 people with an average age of 73, including 24 people with sleep apnea.

When people had lower levels of oxygen due to sleep apnea in REM sleep, their brain scans tended to show higher levels of damaged white matter tissue. 

White matter plays a crucial role in communication between different regions of the brain, and also is involved in learning and memory.

Total time spent sleeping with blood oxygen levels lower than 90% predicted the amount of white matter damage in people’s brains, researchers found. 

Further, people with more white matter damage tended to have shrinkage of brain regions associated with memory like the hippocampus and the entorhinal cortex, researchers found.

People with more shrinkage of the entorhinal cortex did worse on memory tests, researchers added.

“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,” Mander said.

Researchers emphasized that the study does not prove that sleep apnea causes the degeneration, only that there's a link.

More information

The Sleep Foundation has more on REM sleep.

SOURCE: American Academy of Neurology, news release, May 7, 2025