A short afternoon nap can be a natural and pleasant thing, especially as we age. But a study published in Alzheimer's & Dementia suggests that when daytime naps become longer and more frequent over time, they may be telling us something important about brain health.

The study examined the relationship between daytime napping and the risk of developing Alzheimer's dementia. The key finding was particularly interesting: The relationship may be bidirectional. On the one hand, longer and more frequent naps were associated with a higher risk of later Alzheimer's. On the other hand, the progression of Alzheimer's further accelerated the increase in nap duration and frequency.

Simply put: more sleep during the day can be both an early sign of brain change — and the result of a process that is already beginning to occur in the brain.

What did they investigate?

The researchers used data from 1,401 participants from the Rush Memory and Aging Project, a long-term study that follows adults into old age.

Unlike many studies that rely on self-reporting, here the researchers used a relatively objective measurement: the participants wore an actigraphy device, a kind of watch-like movement sensor, which can be used to assess when they are sleeping or napping during the day.

Follow-up lasted up to 14 years. The researchers examined how nap duration and nap frequency changed with age, and whether these changes were associated with the onset of Alzheimer's dementia.

What did they find?

The researchers found that as people got older, they tended to nap more during the day—both for longer and more frequently. This in itself is not surprising, as changes in sleep are common in older age.

But in people who developed Alzheimer's, the increase in nap duration and frequency was much faster. According to the researchers, the progression of Alzheimer's disease more than doubled the annual rate of increase in nap duration and frequency.

In addition, longer and more frequent naps were associated with a higher risk of developing Alzheimer's-type dementia later in life. The researchers also found a bidirectional relationship over time: more naps per day were associated with poorer cognitive function a year later, and poorer cognitive function was associated with more naps per day the following year.

What are the conclusions?

The study does not prove that napping causes Alzheimer's. This is a very important point. It is possible that the increased napping is not the cause of cognitive decline, but rather one of the early signs that something is changing in the brain.

The researchers suggest two main possibilities: it is possible that increased sleepiness itself contributes to disrupted sleep-wake cycles and cognitive impairment; and it may primarily reflect early Alzheimer's brain processes, which affect areas of the brain responsible for alertness, sleep, and circadian rhythm.

This means that you shouldn't be alarmed by every afternoon nap, but it is worth paying attention to the change: a person who didn't usually fall asleep during the day, and now falls asleep repeatedly, sleeps for hours during the day, or has difficulty staying awake for no apparent reason — this is a change worth checking out.

What are the recommendations for the public?

The message to the public is not “don’t nap in the afternoon.” A short nap, especially if taken relatively early in the day and does not interfere with nighttime sleep, can be a natural part of life.

But excessive, prolonged, or new napping in older age may be a sign worth investigating. It is important to check whether there is a medical cause: poor quality sleep at night, sleep apnea, depression, pain, side effects of medications, inactivity during the day, underlying diseases, or cognitive changes.

Families are advised to pay attention not only to forgetfulness, but also to changes in sleep and alertness patterns. If an older person begins to sleep much more during the day, wakes up tired, loses interest in activities, or seems less alert, it is a good idea to contact your family doctor or a memory clinic for a proper evaluation.

The main message from the study:

Napping isn't a problem in itself. But daytime naps that become longer, more frequent, or unusual compared to the past may be an early sign of a change in brain health. The study suggests a two-way relationship: more napping is linked to a higher risk of Alzheimer's, and Alzheimer's itself may lead to more daytime napping.

The full article:

• Link:
  https://doi.org/10.1002/alz.12636
  
  

• Reference:

Li, P., Gao, L., Yu, L., Zheng, X., Ulsa, MC, Yang, H.-W., Gaba, A., Yaffe, K., Bennett, DA, Buchman, AS, Hu, K., & Leng, Y. (2022). Daytime napping and Alzheimer's dementia: A potential bidirectional relationship. Alzheimer's & Dementia, 18 (11), 2287–2298. https://doi.org/10.1002/alz.12636

The content is intended to make scientific information accessible to the public and does not constitute medical advice.