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Older women with sleep apnoea may be more likely to develop memory problems and dementia, according to a new study.
It's not clear yet whether treating the sleep apnoea can help prevent that memory decline – but researchers say that question should be addressed.
"It makes sense that good sleep is going to be protective to the brain," said Dr Robert Thomas, who studies sleep at Harvard Medical School in Boston and was not involved in the new study.
But, he added, there's been a lack of information on a link between sleeping problems and memory. "We simply don't have data to answer many of the simple questions people may have in the sleep clinic," he told Reuters Health.
Race and weight play a part in sleep apnoea
In a study reported in online in the Journal of the American Medical Association, Dr Kristine Yaffe of the University of California, San Francisco and colleagues gave overnight sleep apnoea tests to 298 women without dementia, who were an average of 82 years old.
Just over a third of the women tested positive.
About five years later, the researchers brought those same women in for a set of thinking and memory tests, and doctors evaluated any of the women who showed signs of memory decline.
In total, 36% of the women were diagnosed with mild cognitive impairment or dementia.
Among women who had shown signs of sleep apnoea on their overnight tests five years earlier, 45% had developed thinking and memory problems, compared to 31% of women who didn't have sleep problems.
When Dr Yaffe and her colleagues took factors such as race, weight, and other diseases and medications into consideration, women with sleep apnoea were almost twice as likely to test positive for cognitive impairment or dementia.
More health issues linked to sleep apnoea
Sleep apnoea has also been linked to a host of other health problems, including high blood pressure and cholesterol. Researchers pointed to lower blood flow to the brain during sleep as a possible culprit in cognitive problems down the line.
Indeed, when the authors looked at the specific factors that went into a diagnosis of sleep apnoea, they found that the lack of steady oxygen overnight was related to thinking and memory problems, not how much total sleep women got or how many times they woke up during the night.
Researchers still don't know to what extent treatment of sleep apnoea can prevent complications, including cognitive decline.
"The single biggest hole in sleep apnoea research is, what are the outcomes of treatment?" Dr Thomas said.
Dr Yaffe agreed. "That's obviously a next step and important question," she told Reuters Health.
(Reuters Health, August 2011)
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