Taking short naps during the day could well be the key to helping to protect the brain's health as we age and help to reduce the risk of developing dementia.
It's thought the practice helps preserve brain volume, a quality linked with healthy cognitive functions and a lower risk of not just dementia, but also other diseases.
Previous research suggested long naps could be an early symptom of Alzheimer's disease, but the latest research reveals that brief snoozes can improve people's ability to learn and fight against brain shrinkage.
That's interesting because while our brains shrink with age, the process is accelerated in people with cognitive issues and neurodegenerative diseases, with some research even suggesting it could be linked to sleep issues.
Scientists from the US, UK, and Uruguay analysed data from 378,932 people aged between 40 and 69 to see how those who are genetically 'programmed' to nap regularly fared cognitively compared to those who lacked comparable genes.
These variants are set at birth and assumed to be randomly assigned, which allows researchers to look into the effect napping can have on the brain by reducing the impact of lifestyle factors that can influence napping habits and brain health - such as smoking or physical activity.
"It is like a natural randomised control trial," said Dr Victoria Garfield, a co-author of the study. Dr Garfield added the variants were quite common.
"They're present in around at least one per cent of the population, which is actually quite a lot of people."
Those who partake in a daytime snooze, they found, had larger brains equivalent to those who are anywhere between 2.6 and 6.5 years younger.
Lead author Valentina Paz, a neuroscientist at University College London (UCL) said: "Our study points to a causal link between habitual napping and larger total brain volume."
While it first appeared that participants who reported never or rarely having a daytime nap had a larger total brain volume, the team found the reverse relationship when genetic predisposition to napping was taken into account.
It suggests the initial finding could have been down to other factors, which muddies the relationship between catching 40 winks during the day and brain size.
"It could be having a short daytime nap... could help preserve brain volume and that's a positive thing, potentially, [for] dementia prevention," said Dr Garfield.
Dr Garfield added that while there were a plethora of risk factors that could lead to dementia, with multiple other factors also affecting brain volume.
It's also worth noting that the study is based on data only from white British people, and the exact duration of naps associated with the benefits are unclear.
Prior studies suggest naps less than 30 minutes are best, with earlier naps in the day less likely to affect sleep at night. It is also unclear whether the same benefits of napping would be seen in those who don't have the predisposition.
