Study links increasing sleepiness, higher dementia risk among older women

Women in their 80s who experience increasing sleepiness over time have double the risk of developing dementia than their counterparts with stable sleep patterns, a recent analysis suggests. Published in Neurology, the study looked at data from 733 women without cognitive impairment who participated in a study that ran between 2002 and 2009. The women were a mean of 82.5 years old at the start of the study, and they used a wrist device that tracked their sleep and circadian rhythm patterns over three consecutive days once at the start of the study and again five years later. Patients filled out sleep logs and were given neuropsychological tests during the five-year follow-up.

On average, participants’ total sleep time increased by 18.7 minutes during the five-year follow-up period, and sleep efficiency — a score of sleep quality — increased by 0.94 percent on average. Napping rose over the study period, too, with participants’ napping duration increasing 33.1 minutes.

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About 44 percent of the women showed stable sleep patterns during the study. Another 34.9 percent were categorized as having declining nighttime sleep, with decreased nighttime sleep quality and slight increases in daytime napping. The final group, which made up 21.3 percent of the women, saw “large increases in daytime and nighttime sleep duration and quality,” the researchers wrote.

Overall, 93 of the women — 12.7 percent — developed dementia during the study period. Those in the groups with declining nighttime sleep or large increases in sleep duration and quality were at a 2-to-3-fold higher risk of developing dementia than the women who had stable sleep.

When the researchers adjusted for demographics such as age, education, race and some health conditions, they found that those in the increased sleepiness group had double the dementia risk compared with stable sleepers. Those with declining nighttime sleep didn’t have as strong an association with dementia when the data was adjusted.

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The study does not prove that increasing sleepiness causes dementia, but the researchers say the association can indicate that changes in sleep over time reveal that a woman is at higher risk for dementia.

“We observed that sleeping, napping and circadian rhythms can change dramatically over only five years for women in their 80s,” Yue Leng, an associate professor in psychiatry at the University of California at San Francisco and the study’s senior author, said in a news release. “This highlights the need for future studies to look at all aspects of daily sleep patterns to better understand how changes in these patterns over time can be linked to dementia risk.”

Because more than 90 percent of the study participants were White women, the researchers say more research is needed to determine whether the same association exists in non-White women.