Can Longer Daytime Naps Be an Early Sign of Dementia?

After a bad night’s sleep, doctors often recommend power naps to recover and last until the following night. But in older people, longer nap times could be an early sign of dementia.

So far, research aimed at determining how napping affects cognition in adults has had mixed results. Some studies seem to suggest that napping is beneficial for cognition in young adults. On the contrary, others conducted on older adults suggest that napping may be associated with the onset of cognitive impairment.

In Older Adults, Napping May Be Linked to Occurrence of Cognitive Impairment – ​​pxhere.com CC0

However, many of these studies rely only on self-reported data. In some cases, however, this methodology may not be precise enough: people with cognitive impairments in particular may have difficulty providing reliable information about the duration or frequency of their naps.

As an epidemiologist studying sleep and neurodegeneration in the elderly, I have investigated whether changes in sleep patterns could be predictors of cognitive decline. The results I received with my collaborators show that it is normal for nap duration to increase with age, but that excessive stretching could well be a sign of cognitive decline.

VIDEO : Sleep and Alzheimer’s May Be Linked (VO with subtitles)

Link between napping and dementia

Difficulty sleeping and inappropriate naps are well-known symptoms associated with mild to moderate forms of Alzheimer’s disease and other forms of dementia in the elderly. As the disease progresses, these symptoms often become more extreme: patients are less and less able to fall asleep when they go to bed, wake up more frequently at night and are therefore more sleepy during the day.

To examine the link between napping and dementia, my colleagues and I studied a group of 1,401 people with an average age of 81 years. These people participated in the project Rush Memory and Aging, a longitudinal study analyzing cognitive decline and Alzheimer’s disease. For fourteen years, participants wore a watch-like device designed to track their mobility. Periods of prolonged inactivity were interpreted as naps.

The Rush Memory and Aging project aimed to analyze cognitive decline and Alzheimer's disease
The Rush Memory and Aging Project aimed to analyze cognitive decline and Alzheimer’s disease – Drphuc/Pixabay

At the start of the study, about 75% of the patients showed no signs of cognitive decline. Of the other patients, 4% had Alzheimer’s disease and 20% had moderate cognitive decline, which is often a precursor to the risk of developing dementia.

Over the years, the daily nap length increased for all participants, but we found differences between people with Alzheimer’s disease and those without. The participants who did not develop cognitive impairment increased their naps by an average of 11 minutes per year.
For those diagnosed with moderate cognitive impairment, that length more than doubled, increasing nap length by an average of 25 minutes per year. Finally, in participants who were diagnosed with Alzheimer’s, this increase tripled again, averaging an additional 68 minutes per year.

Ultimately, we found that older people who napped at least once a day or slept more than an hour during the day were 40% more likely to develop Alzheimer’s disease than those who didn’t, didn’t take a daily nap, or those who did Naps that lasted no more than an hour. These results remained unchanged even after correcting for factors such as daily activities, illness, or medication use.

Napping is part of the normal aging process, provided its duration is not excessively prolonged
Napping is part of the normal aging process, provided its duration is not excessively prolonged – Tom Ang/Photodisc – Getty Images (via The Conversation)

Napping and the “Alzheimer’s” Brain.

Our study shows that longer naps are a normal part of aging, but only to a certain extent. Our colleagues at the University of California, San Francisco have identified a mechanism that could explain why people with dementia sleep more and longer.

They performed the postmortem comparison of the brains of people who died without being affected by cognitive decline with the brains of people affected by Alzheimer’s disease. The results showed that in the latter three brain regions harbored fewer nerve cells (neurons) involved in wakefulness. These neuronal changes appear to be linked to the presence of tau protein aggregates, markers of Alzheimer’s disease, that form when tau protein, which helps stabilize healthy neurons, forms clumps that eventually impede communication between neurons.

Although our study does not show that longer naps lead to cognitive decline, it does indicate that longer naps are a potential signal of accelerated aging. Further research would show whether monitoring the duration of naps could help better detect the onset of cognitive decline.

This analysis was authored by Yue Leng, Assistant Professor of Psychiatry at the University of California (San Francisco).
The original article has been translated (from English) and published on the website of The conversation.

Declaration of Interest
● Yue Leng receives financial support from the National Institute on Aging.

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