Feely sleepy all the time could be a sign of dementia, experts warn.
University of California researchers have uncovered a link between daytime drowsiness and a twofold higher risk of dementia in older women.
Sleep is crucial for neurological health and rejuvenation, as well as the consolidation of new memories and information.
Dementia has been shown to disrupt that process, meaning even those who get eight hours of sleep per night may not be getting quality rest.
The researchers found the link, though they could not say conclusively whether bad sleep causes dementia by circumventing the brain’s normal waste-removal and rejuvenation processes while it sleeps, or if progressive brain decay causes poor sleep quality.
Dr Yue Leng, an epidemiologist at UC San Francisco who specializes in the link between sleep and neurodegeneration in older adults, said: ‘Our study found that sleep problems may be intertwined with cognitive aging and may serve as an early marker or risk factor for dementia in women in their 80s.’
Getting enough quality, uninterrupted sleep – typically between seven and nine hours – fosters better concentration and motivation to learn and work
The researchers from UC San Francisco and UC San Diego analyzed data from the Study of Osteoporotic Fractures (SOF), which enrolled women 65 and up from Baltimore, Minneapolis, Pittsburgh, and Portland, Oregon, between 1986 and 1988.
The study followed 733 women with an average age of 83 at the start over decades.
None of the women exhibited signs of cognitive impairment at the start of the study. Researchers conducted follow-up ‘visits’ at various time points.
They relied on a technology introduced after the study began, specifically around 2002, during the eighth visit.
At that point, researchers began using wrist-worn actigraphs – small devices that measure movement using a sensor and continuously record sleeping and waking activity.
Women wore them for three days at the start and end of the study.
They also conducted cognitive testing periodically throughout the study.
Over a third of the women had declining nighttime sleep (DNS), indicating poor sleep quality.
researchers found that participants in the increasing sleepiness group had double the risk of dementia compared to those in the stable sleep group
Twenty-one percent had increasing sleepiness (IS), and overall, more than half of women had poor sleep patterns over five years.
Over 22 percent of women developed cognitive impairment over a five-year follow-up period, and 13 percent of them developed dementia.
Women stuck in one of these detrimental sleep patterns had a two- to three-fold risk of developing dementia compared to those with stable sleep.
Even after adjusting for age, education, and race, the increased risk of dementia linked to daytime sleepiness was still double.
Using actigraphy data, researchers were also able to see clearly how sleep habits and patterns change as women age.
Both DNS and IS pattern groups napped more during the day, had weaker circadian rhythms, and worsened sleep quality by the year.
The latest research was published in the journal Neurology.
Studies have long questioned the link between sleep patterns and dementia risk, likening it to a chicken-or-the-egg scenario: does poor sleep cause dementia, or does dementia engender poor sleep?
The table shows how five-year changes in sleep patterns are linked to mild cognitive impairment (MCI) and dementia in older women. Women with Declining Nighttime Sleep (DNS) had a 2.03x higher risk of dementia, while those with Increasing Sleepiness (IS) had the highest risk at 2.85x
Several other studies have demonstrated links between insufficient amount of sleep and dementia risk.
A Harvard Medical School study, for instance, followed 2,800 people 65 and older and found those who slept for five hours or fewer every night were twice as likely to develop dementia compared to those who slept six to eight hours nightly.
At the same time, poor sleep is a known symptom of dementia. People with the neurodegenerative disease – around two-thirds of whom are women – often struggle to fall asleep and stay asleep.
People with dementia spend less time in stages three and four of sleep, when the body repairs tissues, bolsters the immune system’s preparedness, processes memories, restores energy, and clears waste products from the brain.
Dr Leng said: ‘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.’
