Do You Feel Sleepy During the Day? In Some Older People, This is Associated With a Twofold Increase in the Risk of Developing Dementia

In women in their 80s, increasing sleepiness during the day over a five-year period was associated with a twofold increased risk of developing dementia during that time. This is according to a study published online in Neurology^®, the medical journal of the American Academy of Neurology. The study does not prove that daytime sleepiness causes dementia; it only shows an association.

How Sleep Changes Increase Dementia Risk

“Sleep is essential to cognitive health because it allows the brain to rest and rejuvenate, improving our ability to think clearly and recall information,” said study author Yue Leng, PhD, of the University of California, San Francisco. However, little is known about how changes in sleep and cognition over time are related and how these changes are associated with the risk of developing dementia in later life. The 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.

For the study, the researchers examined 733 female participants with an average age of 83 years who did not have mild cognitive impairment or dementia at the start of the study. They were observed for five years. During the study, 164 participants, or 22 percent, developed mild cognitive impairment and 93 participants, or 13 percent, developed dementia. Participants wore wrist devices for three days at the beginning and end of the study to track their sleep and circadian rhythm patterns.

Researchers looked at changes in nightly sleep duration and quality, daytime napping and circadian rhythm patterns. After five years, researchers observed major changes in sleep patterns in more than half of the participants (56%). Researchers found that participants could be categorized into three groups: stable sleep or slight improvements in sleep (44%), decreasing nighttime sleep (35%) and increasing sleepiness (21%). Symptoms of decreasing nighttime sleep included a decrease in sleep quality and duration, a moderate increase in naps and a worsening of the circadian rhythm. Symptoms of increasing sleepiness included an increase in sleep duration and quality, both during the day and at night, as well as a worsening of the circadian rhythm.

Future Studies are Important to Examine All Aspects of Daily Sleep Patterns

The researchers then examined how these changes were related to the risk of developing dementia. Of the people in the group with stable sleep, 25, or 8%, developed dementia. In the group with decreasing nighttime sleep, 39, or 15%, developed dementia. In the group with increasing sleepiness, 29, or 19%, developed dementia. After taking into account age, education, ethnicity and health factors such as diabetes and high blood pressure, the researchers found that participants in the group with increasing sleepiness had double the risk of dementia compared to those in the group with stable sleep. No connection was found in the group with decreasing nighttime sleep.

Researchers were able to observe that sleep, naps and circadian rhythms in women in their 80s can change dramatically over just five years. This highlights the need for future studies that examine all aspects of daily sleep patterns to better understand how changes in these patterns over time may be linked to risk of dementia. One limitation of the study was that it included mostly white individuals, so the results cannot be generalized to more diverse populations.