Researchers link OSA, cognitive decline 

IRVINE, Calif. - Obstructive sleep apnea during the rapid-eye movement stage of sleep is linked to early signs of brain changes that are associated with cognitive decline, according to a new study published in the journal Neurology. Neurobiologists at the University of California, Irvine, suggest in the study that low oxygen levels – known as hypoxemia – during REM sleep, when most memory consolidation occurs, may contribute to injury in regions of the brain regions that are vital for memory, even in older adults without cognitive impairment. While the findings do not prove that sleep apnea causes this degeneration, it does show an association, researchers say. “Sleep apnea is important because low oxygen levels during sleep can harm the ability of our brain and bodies to function properly,” said co-corresponding author Bryce A. Mander, PhD, an assistant professor of psychiatry and human behavior at the UC Irvine School of Medicine. “Obstructive sleep apnea is a sleep disorder that increases with age. Our study found that low oxygen levels from obstructive sleep apnea may be linked to cognitive decline due to damage to the small blood vessels in the brain and the downstream impact of this damage on parts of the brain associated with memory.” The study, which received support from the National Institutes of Health, followed 37 people with an average age of 73 who did not have cognitive impairment. They participated in overnight sleep studies and received advanced brain imaging. Of the group, 24 people had obstructive sleep apnea. The researchers discovered that lower oxygen levels during REM sleep — not just the number of breathing interruptions — were most strongly linked to increased white matter hyperintensities, especially in the frontal and parietal lobes. These brain regions are highly active during REM sleep and especially vulnerable to low oxygen. This vascular damage was also associated with thinning in the entorhinal cortex, a brain area often affected early in Alzheimer’s disease. The study stresses that more research is needed in larger, more diverse populations and in people with more severe forms of obstructive sleep apnea.