New Study Links Sleep Apnea to Brain Damage

A recent study suggests that obstructive sleep apnea may be connected to brain damage in areas important for memory. This seems to stem from low oxygen levels experienced during REM sleep. Researchers found that individuals with decreased oxygen saturation during these periods exhibited more white matter hyperintensities—indications of minor blood vessel damage—in brain scans.

This damage was notably linked to a smaller size in the hippocampus and the entorhinal cortex, both vital for memory function, and was associated with poorer outcomes in memory assessments. While the results don’t establish a direct cause-and-effect relationship, they shed light on how sleep apnea might influence cognitive decline and memory impairment, particularly in aging populations and those with Alzheimer’s disease.

Key Facts:

• Oxygen Levels and Brain Health: Low oxygen during REM sleep is tied to small vessel damage in the brain.
• Memory Areas Impacted: Damage correlates with reduced size in memory-related brain regions.
• Cognitive Implications: These alterations in the brain are linked to poorer memory performance dependent on sleep.

Obstructive sleep apnea, a condition that leads to reduced oxygen levels during sleep, has been correlated with the deterioration of brain regions tied to memory, largely due to damage inflicted on small blood vessels. This finding appears in a study that was published online on May 7, 2025, in Neurology.

The study’s findings reveal a strong connection between the severity of oxygen level drops during REM sleep and the brain changes observed. It’s essential to note that the research does not conclusively demonstrate that sleep apnea causes this brain degeneration; it simply identifies a correlation.

Obstructive sleep apnea happens when the muscles in the throat relax excessively during sleep, causing airway blockages that lead to frequent awakenings to breathe. This interrupted sleep pattern can significantly reduce oxygen levels, posing a risk to the small blood vessels in the brain.

REM sleep is notably important as it’s the phase where most dreaming occurs and is linked with memory consolidation and processing emotions.

As Dr. Bryce A. Mander from the University of California Irvine points out, “Obstructive sleep apnea is a disorder that tends to increase with age, and the resulting low oxygen during sleep can adversely affect how our brain and body operate.” He further states that their findings indicate that low oxygen levels during REM sleep may be associated with cognitive decline due to damage to cerebral blood vessels and the subsequent effects on memory-related brain areas.

The study involved 37 participants with an average age of 73, none of whom had cognitive impairments, and none were taking sleep medications. They underwent overnight sleep monitoring, which included measuring their oxygen levels across all sleep phases, particularly REM sleep, along with brain scans to assess structural changes.

Researchers discovered that lower oxygen levels during REM sleep corresponded to increased white matter hyperintensities in the brain, which appear as brighter spots on scans indicating white matter damage. This damage likely arises from injury to small brain blood vessels.

Alarming results showed that blood oxygen saturation dropping to 90% or lower predicted the presence of these hyperintensities.

Additionally, researchers examined the volume of the hippocampus and the thickness of the entorhinal cortex, both associated with memory. Findings suggested that heightened white matter hyperintensities were correlated with decreased size and thickness in these regions.

Before and after sleep, participants also took memory tests to assess sleep-related memory performance. The results highlighted that deficits in sleep-dependent memory were linked to reduced thickness of the entorhinal cortex.

In summary, as Dr. Mander notes, “Our results may shed light on how obstructive sleep apnea contributes to cognitive decline related to aging and Alzheimer’s disease through the deterioration of brain regions critical for memory consolidation during sleep.”

One limitation noted in the study is the demographic homogeneity; most participants were white and Asian, so results may differ for other ethnic groups.

Funding:

This research received support from the National Institute on Aging and the American Academy of Sleep Medicine Foundation.