Regular napping linked to larger brain volume
Daytime napping may help to preserve brain health by slowing the rate at
which our brains shrink as we age

Date:
June 20, 2023
Source:
University College London
Summary:
A study analyzed data from people aged 40 to 69 and found a causal
link between habitual napping and larger total brain volume --
a marker of good brain health linked to a lower risk of dementia
and other diseases.


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FULL STORY ========================================================================== Daytime napping may help to preserve brain health by slowing the rate at
which our brains shrink as we age, suggests a new study led by researchers
at UCL and the University of the Republic in Uruguay.

The study, published in the journal Sleep Health, analysed data from
people aged 40 to 69 and found a causal link between habitual napping
and larger total brain volume -- a marker of good brain health linked
to a lower risk of dementia and other diseases.

Senior author Dr Victoria Garfield (MRC Unit for Lifelong Health & Ageing
at UCL) said: "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." Previous research has shown that napping
has cognitive benefits, with people who have had a short nap performing
better in cognitive tests in the hours afterwards than counterparts who
did not nap.

The new study aimed to establish if there was a causal relationship
between daytime napping and brain health.

Using a technique called Mendelian randomisation, they looked at 97
snippets of DNA thought to determine people's likelihood of habitual
napping. They compared measures of brain health and cognition of people
who are more genetically "programmed" to nap with counterparts who did
not have these genetic variants, using data from 378,932 people from
the UK Biobank study, and found that, overall, people predetermined to
nap had a larger total brain volume.

The research team estimated that the average difference in brain volume
between people programmed to be habitual nappers and those who were not
was equivalent to 2.6 to 6.5 years of ageing.

But the researchers did not find a difference in how well those programmed
to be habitual nappers performed on three other measures of brain health
and cognitive function -- hippocampal volume, reaction time and visual processing.

Lead author and PhD candidate Valentina Paz (University of the Republic (Uruguay) and MRC Unit for Lifelong Health & Ageing at UCL) said: "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 randomisation 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." Dr Garfield added:
"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." The genetic variants influencing our likelihood to nap were identified in an earlier study looking at data from 452,633 UK Biobank participants. The study, led by Dr Hassan Dashti (Harvard University
and Massachusetts General Hospital), also an author on the new study, identified the variants on the basis of self-reported napping, and this
was supported by objective measurements of physical activity recorded
by a wrist-worn accelerometer.

In the new study, researchers analysed health and cognition outcomes for
people with these genetic variants as well as several different subsets
of these variants, adjusted to avoid potential bias, for instance avoiding variants linked to excessive daytime sleepiness.

Genetic data and magnetic resonance imaging (MRI) scans of the brain were available for 35,080 individuals drawn from the larger UK Biobank sample.

In terms of study limitations, the authors noted that all of the
participants were of white European ancestry, so the findings might not
be immediately generalisable to other ethnicities.

While the researchers did not have information on nap duration, earlier
studies suggest that naps of 30 minutes or less provide the best
short-term cognitive benefits, and napping earlier in the day is less
likely to disrupt night-time sleep.

Previous research looking at the UK and the Netherlands found that nearly
a third of adults aged 65 or over had a regular nap.

The study was supported by Diabetes UK, the British Heart Foundation
and the Diabetes Research and Wellness Foundation. In Uruguay it was
supported by Programa de Desarrollo de las Ciencias Ba'sicas (PEDECIBA, MEC-UdelaR), Agencia Nacional de Investigacio'n e Innovacio'n (ANII),
Comisio'n Sectorial de Investigacio'n Cienti'fica (CSIC, UdelaR), and
Comisio'n Acade'mica de Posgrados (CAP, UdelaR). In the United States
it was supported by the National Heart, Lung, and Blood Institute.

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========================================================================== Story Source: Materials provided by University_College_London. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Valentina Paz, Hassan S. Dashti, Victoria Garfield. Is there an
association between daytime napping, cognitive function, and brain
volume? A Mendelian randomization study in the UK Biobank. Sleep
Health, 2023; DOI: 10.1016/j.sleh.2023.05.002 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/06/230620113759.htm

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