People who experience certain breathing problems at night may be more likely to develop cognitive impairment than individuals without any difficulties breathing while they sleep, a research review suggests.
Data obtained from 14 previously published studies with a total of more than 4.2 million men and women showed that people with sleep-disordered breathing had 26% higher odds of developing cognitive impairment, researchers report in JAMA Neurology, online August 28.
“Identification of this sleep disorder in elderly persons might help predict future risk of cognitive impairment and thus is important for the early detection of dementia,” said lead study author Yue Leng of the University of California, San Francisco.
“Moreover, sleep-disordered breathing is a treatable disease,” Leng said by email. “If sleep-disordered breathing is a risk factor for dementia, then treatment of sleep-disordered breathing might benefit cognition and help reduce the risk of dementia in the long run.”
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Many people with nighttime breathing problems had sleep apnea. Risk factors for sleep apnea include older age and obesity.
In the smaller studies included in the analysis, the increased risk of cognitive impairment associated with sleep-disordered breathing ranged from 23% to 86%.
When researchers analysed the increased risk across all of the smaller studies with a similar design, excluding one that was done much differently, the overall increased risk of cognitive impairment associated with sleep-disordered breathing was 35%.
Sleep-disordered breathing was also associated with slightly worse “executive function” – that is, the mental processes involved in planning, paying attention, following instructions, and multi-tasking, for example - but it didn’t appear to influence memory, the study also found.
The researchers had only limited data on executive function, however, which made it difficult to determine whether any changes associated with sleep-disordered breathing might be clinically meaningful.
The analysis also didn’t account for obesity, which is independently a risk factor for both apnea and cognitive impairment, noted Marie-Pierre St-Onge, a researcher at Columbia University Medical Center in New York City who wasn’t involved in the study.
“It’s possible that the reduction in oxygen reaching the brain from apnea could, over time, lead to brain injuries that can lead to cognitive impairment,” St-Onge said by email. “There is also a link between obesity and mild cognitive impairment and between obesity and sleep-disordered breathing.”
Shedding excess weight might help, said Hui-Xin Wang of the Karolinska Institute in Stockholm.
“Weight-loss strategies, including physical exercise and diet, have been evaluated as a treatment strategy to improve sleep-disordered breathing and reduce the risk of cognitive decline,” Wang, who wasn’t involved in the study, said by email.
Beyond weight loss, treatments for apnea may include wearing a breathing mask or jaw support at night to keep airways open.
More research is needed, however, to determine whether and to what extent treating sleep apnea might lower the risk of cognitive decline, said Kristen Knutson of the Center for Circadian and Sleep Medicine at the Northwestern University Feinberg School of Medicine in Chicago.
“There are therapies available for apnea that would improve sleep and potentially improve health, including cognitive function,” Knutson, who wasn’t involved in the study, said by email. “People who have trouble sleeping or who snore loudly and frequently should raise this issue with their doctors and discuss potential treatments.”