06-26-2023

Regular daytime napping increases brain health

Earth.com staff writer

A team of researchers led by University College London (UCL) and the University of the Republic of Uruguay has recently analyzed data from a large cohort of people aged 40 to 69 and found a causal link between regular daytime napping and larger total brain volume – a well-known marker of brain health leading to a lower risk of dementia and other neurodegenerative diseases. This surprising finding suggests that habitual napping may help preserve brain health by slowing the rate at which our brains shrink as we age.

“Our findings suggest that, for some people, short daytime naps may be a part of the puzzle that could help preserve the health of the brain as we get older,” said study senior author Victoria Garfield, an expert in Genetic Epidemiology at UCL.

Although previous research has found that daytime napping has significant cognitive benefits – with people who had a short nap performing better in cognitive tests in the hours after the nap than those who stayed awake – this study is the first to identify a causal relationship between naps and brain health.

How the research was conducted

To determine people’s likelihood of habitual napping, the scientists used a technique called Mendelian randomization to examine 97 snippets of DNA. This statistical method is generally used in Epidemiology and Genetics to investigate the causal relationship between an exposure or risk factor and an outcome or disease. The technique is focused on sets of genetic variants that are randomly assigned at conception and are not influenced by environmental and confounding factors.

Then, by using data from 378,932 participants from the UK Biobank, they compared measures of brain health and cognition of people who were more genetically prone to nap with counterparts without these genetic variants. The genetic variants influencing our likelihood to nap were identified in an earlier study (based on data from 452,633 UK Biobank participants) through self-reported napping combined with objective measurements of physical activity recorded by wrist-worn accelerometers.

What the researchers discovered

The analysis revealed that participants predetermined to nap had a larger total brain volume, with the average difference in volume between people “programmed” to be habitual nappers and those who were not being equivalent to between 2.5 to 6.5 years of aging. Although the researchers did not have information on nap duration, earlier studies suggest that short naps (of half an hour or less) provide the best cognitive benefits, while napping earlier in the day is less likely to disrupt night-time sleep.

“This is the first study to attempt to untangle the causal relationship between habitual daytime napping and cognitive and structural brain outcomes. By looking at genes set at birth, Mendelian randomization avoids confounding factors occurring throughout life that may influence associations between napping and health outcomes. Our study points to a causal link between habitual napping and larger total brain volume,” said lead author Valentina Paz, an assistant professor of Psychology at the University of the Republic of Uruguay.

“I hope studies such as this one showing the health benefits of short naps can help to reduce any stigma that still exists around daytime napping,” Garfield added.

However, since all the participants were of white European ancestry, the findings might not be immediately generalizable to other ethnicities. In addition, further research is needed to assess how habitual nappers perform on three other important measures of brain health and cognition (hippocampal volume, reaction time, and visual processing). The study is published in the journal Sleep Health.

More about napping and health

Napping can be beneficial to your health in several ways, but like many things, it’s all about balance and moderation. Here are some ways that naps can be good for your health:

Increased alertness

A quick nap, also known as a “power nap,” can help improve your alertness and motor learning skills. This is particularly true if you are very tired or are in need of an alertness boost.

Improved memory and learning

Naps can enhance your memory and cognitive ability. Some studies suggest that napping can improve creative problem-solving and verbal memory, as well as perceptual learning.

Mood enhancement

Napping can also help uplift your mood. Sleep, in general, has a significant influence on your mood, and a brief nap can serve as a quick mood booster during a stressful day.

Reduced fatigue

Daytime naps can help reduce fatigue, increase wakefulness, and enhance performance and learning.

Potential downsides of napping

Sleep inertia

This is a term for the groggy, disoriented feeling that can come after waking up from a deep sleep. If you take a longer nap, you can wake up in the middle of a sleep cycle, which can lead to sleep inertia.

Nighttime sleep problems

Regular, lengthy napping during the day can interfere with nighttime sleep – especially if you’re struggling with insomnia or poor sleep quality at night.

Underlying health issues

Excessive daytime sleepiness, including the desire to take frequent or very long naps, can be a sign of an underlying health condition, like sleep apnea or depression.

Tips for effective napping

Keep it short

Aim to nap for only 10-20 minutes. The longer you nap, the more likely you are to feel groggy afterward.

Choose the right time

The optimal time for napping tends to be in the middle of the afternoon, around 2 or 3 p.m. This helps because it’s often a natural point of drowsiness in the circadian rhythm, and it’s less likely to interfere with nighttime sleep.