Study: Excessive daytime sleepiness may lead to dementia

A new study has suggested that older adults experiencing daytime sleepiness or a lack of enthusiasm for activities due to sleep issues may be at higher risk of developing motoric cognitive risk (MCR) syndrome, a condition that can precede dementia. 

The new research, published on Wednesday in the journal Neurology, found that among participants who experienced excessive daytime sleepiness and a lack of enthusiasm, 35.5% developed MRC syndrome compared with 6.7% of people without those problems.

MCR is a predementia syndrome characterized by slow gait speed and cognitive complaints among older people who don’t already have dementia or a mobility disability. The risk of developing dementia more than doubles in people with this syndrome.

During the study, researchers examined data on 445 adults who were 76 years old on average and had no history of dementia. Participants took questionnaires for sleep and were asked about memory issues. Their walking speed was tested on a treadmill and then once a year for an average of three years.

The researchers assessed the participants’ sleep quality and quantity using the seven components of the Pittsburgh Sleep Quality Index.

The index included subjective sleep quality, time it takes to fall asleep, sleep duration, sleep efficiency (ratio of total hours asleep to total hours in bed), sleep disturbances, use of sleep-inducing medication, and daytime dysfunction, such as having trouble staying awake during activities or feeling less enthusiasm to get things done.

The researchers found that 177 participants met the definition of poor sleepers, while 268 were considered good sleepers. 42 people had MCR at the start of the study, and another 36 developed it.

The study found that people with excessive daytime sleepiness and a lack of enthusiasm for activities were more than 3 times more likely to develop MCR syndrome than people who didn’t have these sleep-related problems.

However, Tara Spires-Jones, professor of neurodegeneration and director of the Centre for Discovery Brain Sciences at the University of Edinburgh in Scotland, said the study has a few “serious” limitations.

“The sleep measurements were self-reported, not measured by a scientist, and these self-reports could be biased by people with memory issues,” Tara said.

“The participants in the study were also largely white, and the group was much smaller than similar single-timepoint studies, so the results will be stronger if confirmed in future studies.”

Victoire Leroy, the study author, said “more research needs to be done to look at the relationship between sleep issues and cognitive decline and the role played by motoric cognitive risk syndrome”.

“We also need studies to explain the mechanisms that link these sleep disturbances to motoric cognitive risk syndrome and cognitive decline,” Leroy, who has an MD, and PhD from Albert Einstein College of Medicine, added.