Sleep Apnea Tied to Higher Levels of Alzheimer Protein

Megan Brooks

March 05, 2019

Obstructive sleep apnea may have a role in tau accumulation in the brain, increasing the risk for Alzheimer disease.

In a cross-sectional study of cognitively normal older adults, researchers found a significant association between sleep apnea and elevated tau positron- emission tomography (PET) signal in the entorhinal cortex.

"Previous prospective studies have shown that patients with sleep apnea are at an increased risk for cognitive impairment and dementia," Diego Z. Carvalho, MD, of the Mayo Clinic, Rochester, Minnesota, told Medscape Medical News. "Our work provides further evidence of this process, suggesting that it may be related to increased accumulation of tau protein in a region of the brain that is very susceptible in Alzheimer's disease."

The study will be presented at the upcoming American Academy of Neurology (AAN) 2019 Annual Meeting.

From the population-based Mayo Clinic Study of Aging, researchers identified 288 cognitively normal persons aged 65 years and older with both tau-PET and amyloid-PET scans. Their bed partners were asked whether they had witnessed episodes of apnea during sleep, and 43 (15%) said they had.

Cases of witnessed apnea were significantly associated with tau in the entorhinal cortex. Specifically, participants with sleep apnea were found to have on average 4.5% higher levels of tau in this region of the brain after controlling for age, sex, years of education, body mass index, hypertension, hyperlipidemia, diabetes, reduced sleep, excessive daytime sleepiness, and global amyloid.

"People who have been observed/witnessed to have stop-breathing events during sleep should seek medical attention for expedited diagnostic evaluation of possible obstructive sleep apnea and start treatment, if indicated," Carvalho told Medscape Medical News.

"Medical providers, particularly at the primary care level, should ask their patients about sleep disorders, particularly witnessed apneas, so patients can be properly assessed and diagnosed," he added.

Additional longitudinal studies should assess whether treatment of sleep apnea using continuous positive airway pressure or other approaches could prevent or slow down the accumulation of tau, Carvalho suggested.

"However, it's also possible that increased tau accumulation could predispose to sleep apnea in the elderly, particularly in different areas of the brain related to sleep and breathing, which should be assessed in further studies," he said.

Hot Topic

Commenting on the study for Medscape Medical News, Neeraj Kaplish, MD, assistant professor of neurology at the University of Michigan Sleep Disorders Center and member of the American Academy of Sleep Medicine, called the abstract "interesting," albeit with "limited information. The sample size was small and lack of any objective testing are other limitations," he said.

Kaplish also noted that sleep disordered breathing occurs at a "much higher frequency" in the age group studied. "Only 15% of the participants had witnessed apneas, though it might be confounded by observer bias or underreporting," he said.

"Sleep and dementia is quite a hot topic in research right now, so it's nice to see more and more work coming out of that particular space," Rebecca Edelmayer, PhD, director of scientific engagement at the Alzheimer's Association, told Medscape Medical News.

This study is "very preliminary," she noted, and the mechanism for the association remains unclear. "Maybe it's related to apnea, or maybe it's related to disruption in circadian rhythm in some way. It's still not known yet, and a lot of researchers are looking into potential mechanisms to try to understand this," said Edelmayer.

"There is evidence behind good sleep being good for brain health overall, and if it's something that you are struggling with, whether it be with apnea or some other cause for sleep disturbances, we would recommend having that conversation with your physician to see if there is a way to restore good sleep into your healthy lifestyle habits," Edelmayer added.

The study was supported by the National Institutes of Health. Carvalho, Kaplish, and Edelmayer have disclosed no relevant financial relationships.

American Academy of Neurology (AAN) 2019 Annual Meeting.

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