People who are witnessed to have stopped breathing during sleep may have higher accumulations of the Alzheimer’s disease biomarker tau in an area of the brain that helps with memory, according to a new study.
Obstructive sleep apnea is a condition that involves frequent events of stopped breathing during sleep, although an apnea may also be a single event of paused breathing during sleep, researchers explain.
“A person normally has fewer than five episodes of apnea per hour during sleep,” said study author Diego Z. Carvalho, M.D., of the Mayo Clinic in Rochester, Minnesota. “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.
“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.”
The study included 288 people age 65 and older who did not have cognitive impairment. Bed partners were asked whether they had witnessed episodes of stopped breathing during sleep.
Participants then had positron emission tomography (PET) brain scans to look for accumulation of tau tangles in the entorhinal cortex area of the brain, an area of the brain in the temporal lobe that is more likely to accumulate tau than some other areas, according to the researchers. This area of the brain helps manage memory, navigation, and perception of time.
Researchers identified 43 participants, 15 percent of the study group, whose bed partners witnessed apneas when they were sleeping.
The researchers found that 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. That was 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, the researchers noted.
“Our research results raise the possibility that sleep apnea affects tau accumulation,” said Carvalho. “But it’s also possible that higher levels of tau in other regions may predispose a person to sleep apnea, so longer studies are now needed to solve this chicken and egg problem.”
Limitations of the study included its relatively small sample size and preliminary nature of the study, requiring future validation, the researchers note. A lack of sleep studies to confirm the presence and severity of sleep apnea and a lack of information regarding whether participants were already receiving treatment for sleep apnea is another serious limitation, they add.
The preliminary study will be presented at the 2019 American Academy of Neurology’s 71st Annual Meeting in Philadelphia.