If you want a big brain, make a habit out of daytime naps

You are getting sleepy… very sleepy

If you're working from home and there's been a lull in things to do, why not take a nap? Heck, even if you're in the office, find a nice quiet corner and close your eyes for 20 minutes because we have good news.

Scientists from UCL and the University of the Republic in Uruguay have found that daytime napping may actually help to reduce the rate at which our brains shrink with age.

This should be of particular interest to the more senior among us as it has been established that ageing causes changes to brain size, vasculature, and cognition, increasing the risk of stroke, white matter lesions, and dementia.

If this is making your eyelids feel heavy, go have a kip – you have our blessing.

The study [PDF] published in the journal Sleep Health crunched data on people aged 40 to 69 and claims to have found "a causal link" between habitual napping and larger total brain volume – a sign of a healthy brain and reduced risk of developing cognition-impairing diseases.

This wasn't a small sample either. The research drew on 378,932 people who had contributed to the UK Biobank database.

Senior author Dr Victoria Garfield, of the 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 demonstrated that napping is beneficial to our brainpower – people who have had a short nap perform better in cognitive tests in the hours following than those who had not, but this study aimed to establish whether there was a causal relationship between daytime napping and brain health.

Through a technique called Mendelian randomization, the boffins examined 97 snippets of DNA believed to determine how likely people are to habitually nap. By comparing measures of brain health and cognition of people more genetically predetermined to nap with those who lacked these genetic variants, they found that the more somnolent tended to have a larger brain volume.

The team reckoned that the difference in brain volume between the two groups equated to between 2.6 and 6.5 years of ageing. But it's not all sunshine and roses. There was no improvement found for habitual nappers in three other measures of brain health – hippocampal volume, reaction time and visual processing.

Lead author and PhD candidate Valentina Paz 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."

One limitation of the study, however, was that all participants were of White European ancestry so the authors cautioned that the findings might not be applicable to other ethnicities. Still, it couldn't hurt to try, could it?

Because the research was carried out on pre-existing data, the scientists did not have information on the length of these naps, but previous studies have given a ballpark figure of 30 minutes or less for the best short-term cognitive benefits. Napping earlier in the day is also a good idea to prevent it from interfering with night-time sleep.

Now, if you'll excuse me, I think I need to lie down. ®

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