Naps can do us the world of good, and give us the second wind we need. But daytime napping could also come with an added bonus: preserving brain health by slowing the rate at which brains shrink as we age.

A study by UCL and the University of the Republic in Uruguay analysed data from people aged 40 to 69 and found a link between habitual napping and bigger brains – a marker of good brain health and linked to a lower risk of dementia and other diseases. Senior author Dr Victoria Garfield, 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 napping has cognitive benefits, with people who have had a short nap performing better in cognitive tests in the hours afterwards than people who didn’t have a light snooze. The new study aimed to establish if there was a causal relationship between daytime naps and brain health – meaning, if one of them caused the other.

When researchers compared brain health and cognition in people who are more genetically “programmed” to nap with counterparts who didn’t have these genetic variants, they found, overall, people predetermined to nap had a larger brain volume. Based on data on 378,932 people from the UK Biobank study, the 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.

Lead author and PhD candidate Valentina Paz, of the University of the Republic, Uruguay, said: “This is the first study to attempt to untangle the causal relationship between habitual daytime napping and cognitive and structural brain 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.”

While the researchers didn’t 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.