The Grapevine

Feeling Very Sleepy During Daytime Linked To Alzheimer's Risk

Adults who feel excessively sleepy during the daytime and are prone to taking naps regularly may be more likely to have a brain marker for Alzheimer's disease compared to those who do not experience daytime sleepiness. 

The study titled "Excessive daytime sleepiness and napping in cognitively normal adults: associations with subsequent amyloid deposition measured by PiB PET" was recently published in the journal Sleep.

"If disturbed sleep contributes to Alzheimer's disease, we may be able to treat patients with sleep issues to avoid these negative outcomes," said Adam P. Spira, associate professor in the Department of Mental Health at the Johns Hopkins Bloomberg School of Public Health, Maryland.

He and his collaborators examined data on more than 100 adults from the Baltimore Longitudinal Study of Aging Neuroimaging Substudy, a long-term study which began in 1958. The participants, aged between 36 and 82, filled out surveys about their sleeping habits and also received positron emission tomography (PET) scans. 

As a part of the questionnaire, they were asked if they often become drowsy or fall asleep during the daytime when wishing to be awake. They were also asked to note the frequency of their naps with the response options of rarely/never, one to two times a week, three to five times a week, and every single day.

The analysis revealed that those who reported excess levels of sleepiness during the daytime were close to three times more likely to have deposits of a protein called beta-amyloid in their brains. Experts have long believed these proteins are associated with Alzheimer’s,  with an increase in deposits driving the development of the disease.

“Factors like diet, exercise, and cognitive activity have been widely recognized as important potential targets for Alzheimer’s disease prevention, but sleep hasn’t quite risen to that status, although that may well be changing,” Spira explained.

While the findings are a step closer to a clearer picture, it is still not known whether daytime sleepiness led to the build-up of beta-amyloid or if it was the other way around. According to previous studies using mice, it was the loss of sleep that increased such formations. But further studies are needed to understand if this causation also applies to human beings.  

With concrete evidence, one can expect to see sleep included as a modifiable risk factor for the disease. Interventions to target insomnia, shift work disorders, depression, obstructive sleep apnea, hormone imbalances, etc. will be a priority.

"There is no cure yet for Alzheimer's disease, so we have to do our best to prevent it. Even if a cure is developed, prevention strategies should be emphasized," Spira said. "Prioritizing sleep may be one way to help prevent or perhaps slow this condition."