Sleep apnea correlated with increased levels of Alzheimer’s biomarker

The chronic sleep disorder known as obstructive sleep apnea, observed in more than three million cases per year in the U.S., might be linked to higher accumulations of tau, a biomarker in the brain linked to Alzheimer’s disease, a preliminary study has found.

“A person normally has fewer than five episodes of apnea per hour during sleep. Bed partners are more likely to notice these episodes when people stop breathing several times per hour during sleep, raising concern for obstructive sleep apnea,” said Dr. Diego Z. Carvalho, author of the study and a researcher at Mayo Clinic in Rochester, Minnesota.

“Recent research has linked sleep apnea to an increased risk of dementia, so our study sought to investigate whether witnessed apneas during sleep may be linked to tau protein deposition in the brain.”

For the study, researchers recruited 288 older adults, aged 65 and older, without the presence of cognitive deficits. Patterns of nocturnal breathing cessations were then surveyed by bed partners.

Researchers then examined accumulations of the protein tau in the entorhinal cortex, an area of the brain in the temporal lobe responsible for memory, navigation, and perception of time, by conducting positron emission tomography (PET) brain imaging scans.

In the findings, 43 participants, or 15 percent of the study group, exhibited episodes of apneas during sleep, according to their bed partners. Moreover, the study also uncovered a 4.5 percent increase in levels of tau in the entorhinal cortex in participants with apneas, compared to those without a sleep disorder.

“Those who had apneas had on average 4.5 percent higher levels of tau in the entorhinal cortex than those who did not have apneas, after controlling for several other factors that could affect levels of tau in the brain, such as age, sex, education, cardiovascular risk factors, and other sleep complaints,” researchers stated, in an American Academy of Neurology (AAN) press release.

“Our research results raise the possibility that sleep apnea affects tau accumulation,” Carvalho added.

Researchers now suggest that higher levels of tau in other regions of the brain could make an individual genetically predisposed to sleep apnea; however, more research is needed to prove this theory.

The study was published by the American Academy of Neurology.

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