Napping Linked to Larger Brain Volume, Study Shows

A recent study found a causal link between habitual napping and larger total brain volume in people aged 40 to 69, a marker associated with higher cognitive and structural brain outcomes and a lower risk for diseases such as dementia.

Researchers from University College London and the University of the Republic in Uruguay conducted the study, published in the journal Sleep Health, which aimed to determine how napping impacts the brain health of middle-aged people.

To do so, researchers used a technique known as Mendelian randomization, which involved the analysis of 97 snippets of DNA thought to predict a person’s propensity for habitual napping. Using data from 378,932 people included in the UK Biobank Study, the researchers compared measures of brain health and cognition of those determined to be genetically inclined to nap with those who were not.

"This is the first study to attempt to untangle the causal relationship between habitual daytime napping and cognitive and structural brain outcomes,” said lead author and PhD candidate Valentina Paz of the University of the Republic in Uruguay. “By looking at genes set at birth, Mendelian randomization avoids confounding factors occurring throughout life that may influence associations between napping and health outcomes.”

The investigation’s findings suggested that overall, those predisposed to napping had larger total brain volume. Researchers estimated that the average difference in brain volume between likely habitual nappers and those less inclined to nap was equivalent to 2.6 years to 6.5 years of aging. However, they found no difference between the two groups in other markers of brain health and cognitive function measured, including hippocampal volume, reaction time, and visual processing.

"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,” said senior author Victoria Garfield, PhD, a senior research fellow at the University of London. "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."