A new 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.
Senior author Dr Victoria Garfield 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.”
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, 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 aging.
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 like 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.”
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.
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
University College London. “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.” ScienceDaily. ScienceDaily, 20 June 2023. <www.sciencedaily.com/releases/2023/06/230620113759.htm>.
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