Can Sleep Apnea Lead to Dementia?
People who have sleep apnea or spend less time in deep sleep may be more likely to have changes in the brain associated with dementia, according to a new study in Neurology.
“Our findings support the idea that low oxygen levels during sleep are the main feature of sleep apnea that affects cognition,” says lead study author Rebecca P. Gelber, MD, DrPH, of the VA Pacific Islands Health Care System and the Pacific Health Research and Education Institute in Honolulu, Hawaii.
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“Low oxygen levels during sleep are commonly seen with sleep apnea and other conditions such as chronic obstructive pulmonary disease,” she says. “Clinicians should keep in mind that how their patients sleep, and how they breathe during sleep, are important for brain function and dementia risk.”
Previous studies had suggested that sleep apnea and low oxygen levels during sleep may lead to dementia, but it was unclear how this may happen, and what pathologic changes in the brain may occur to lead to such memory problems.
In this study, Gelber and her colleagues examined data from the Honolulu-Asia Aging Study, a prospective cohort of 3,374 Japanese American men in Honolulu, Hawaii, who have been followed since 1965.
They examined associations between sleep characteristics and neuropathic lesions at autopsy in 167 of the men who underwent at-home polysomnography in 1999-2000, at an average age of 84.
All of the men were followed until they died an average of 6 years later, and autopsies were conducted on their brains to look for loss of brain cells, plaques and tangles associated with Alzheimer’s disease, Lewy bodies found in Lewy body dementia, and microinfarcts—small abnormalities in brain tissue associated with the development of dementia. Loss of brain cells is also associated with Alzheimer’s disease and dementia.
“We found that low oxygen levels during sleep may lead to more microinfarcts in the brain, which involve changes in the small blood vessels of the brain and injury to the surrounding nerve cells,” Gelber says. “We also found that less time spent in slow-wave sleep, which has been considered the deep, restorative stage of sleep and is important in processing new memories, may lead to more generalized atrophy of the brain.”
This is important because it lends insight into how these brain lesions—which are so common and detrimental to brain function—may develop.
But can health care providers do anything to prevent or slow this cognitive decline?
A previous study showed that use of continuous positive airway pressure treatment for obstructive sleep apnea may improve cognition, even after dementia has developed, but Gelber emphasizes more work needs to be done.
“Further studies are needed to examine how slow-wave sleep may have a restorative role in brain function, and whether prevention of low oxygen levels during sleep may reduce the risk of cognitive decline and dementia,” she says.
—Colleen Mullarkey
Reference
Gelber RP, Redline S, Ross GW, Petrovitch H, Sonnen JA, Zarow C, et al. Associations of brain lesions at autopsy with polysomnography features before death. Neurology. 10 Dec 2014. [Epub ahead of print].