Older women experiencing memory loss are more likely than women without cognitive decline to have problems falling asleep and staying asleep, according to a study.
For the study, 2,474 women with an average age of 69 and no signs of memory problems underwent cognitive tests over 15 years. Sleep problems were measured at the end of the study.
The study found the nearly 25 percent of women who experienced cognitive decline were twice as likely as women without memory problems to experience sleep disturbances.
"For women who declined on either cognitive test, they were nearly twice as likely to have difficulty staying asleep and one-and-half times as likely to have problems falling asleep and being awake for more than 90 minutes during their sleep cycle," said study author Kristine Yaffe, MD, with the University of California, San Francisco, and member of the American Academy of Neurology.
"Women who declined on one of the tests were also nearly twice as likely to nap more than two hours a day."
The study found cognitive decline was not associated with total sleep time.
"Perhaps the most likely reason why memory loss may increase the risk of sleep disturbances is that they share a common underlying cause, such as brain changes seen with Alzheimer's disease or other dementias that could increase risk of both memory loss and sleep problems," said Yaffe. "Another reason could be that women with memory problems may also have anxiety or depression that could affect their sleep. While we attempted to adjust for these measures in our study, it's possible that this effect remains."
Yaffe says their findings are consistent with prior studies that have found an association between sleep disturbances and poor cognitive function. "But our study raises the possibility that cognitive decline may increase the risk of sleep problems, rather than vice versa."
"This study does not mean that an individual with cognitive problems will necessarily develop sleep trouble, but that these elders are at a higher risk of sleep disorders," said Yaffe.
The study was supported by grants from the National Institutes of Health.