A recent study published in Neurology suggests that sleep apnea during the dream stage of sleep, known as REM sleep, may be linked to changes in brain regions responsible for memory.
The research, conducted by scientists at the University of California Irvine, found that people with obstructive sleep apnea, a condition that disrupts breathing during sleep, often experience lower oxygen levels that could damage small blood vessels in the brain.
This damage may, in turn, affect areas involved in memory and cognitive function.
Obstructive sleep apnea happens when throat muscles relax too much during sleep, blocking the airway and causing brief wake-ups to breathe. This interruption reduces oxygen levels in the blood and prevents deep, restful sleep.
REM sleep is particularly important because it is when most dreaming occurs and when the brain processes memories and emotions.
According to study author Bryce A. Mander, Ph.D., low oxygen levels during REM sleep might lead to cognitive decline by damaging small blood vessels in the brain, which then harms memory-related regions.
The study included 37 participants with an average age of 73, none of whom had cognitive impairments or were taking sleep medications.
Among them, 24 had obstructive sleep apnea. Researchers monitored their oxygen levels during all stages of sleep, focusing on REM sleep. Brain scans were also performed to examine brain structure and look for signs of damage.
The scans revealed that participants with lower oxygen levels during REM sleep had more white matter hyperintensities—bright spots on brain scans that indicate damaged brain tissue.
This type of damage is believed to result from injury to small blood vessels.
The researchers also measured blood oxygen levels during sleep, finding that when oxygen levels dropped below 90%, the amount of brain damage increased. A blood oxygen level below 90% is generally considered concerning for health.
The study also looked at specific brain regions associated with memory, including the hippocampus and the entorhinal cortex.
They found that people with more white matter hyperintensities also had reduced volume and thickness in these memory-related areas.
To understand the impact on memory, participants took a memory test before and after sleep. The results showed that those with more brain damage and lower oxygen levels during REM sleep performed worse on memory tests.
Mander explained that these findings might help to understand how obstructive sleep apnea contributes to memory problems and cognitive decline, especially as people age.
He suggested that the damage to small blood vessels in the brain during sleep could be a link between sleep apnea and conditions like Alzheimer’s disease.
However, the study had limitations. Most of the participants were white or Asian, so the results may not apply to other populations.
Despite this, the findings add to growing evidence that sleep apnea may not just disrupt sleep—it might also impact brain health and memory over time.
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