Researchers from UCL and the University of the Republic in Uruguay have conducted a study suggesting that regular daytime napping can contribute to maintaining brain health by slowing down the rate at which our brains shrink as we age. Published in the journal Sleep Health, the study examined data from individuals aged 40 to 69 and discovered a causal link between habitual napping and larger total brain volume, which is considered an indicator of good brain health and lower risk of diseases such as dementia.
Dr. Victoria Garfield, the senior author from the MRC Unit for Lifelong Health & Ageing at UCL, stated, "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 already highlighted the cognitive benefits of napping, showing that individuals who take short naps tend to perform better in cognitive tests afterward compared to those who do not nap.
To establish a causal relationship between daytime napping and brain health, the researchers employed a technique called Mendelian randomisation. They examined 97 snippets of DNA associated with habitual napping tendencies and compared measures of brain health and cognition between individuals genetically predisposed to nap and those without these genetic variants. The study utilized data from the UK Biobank study, encompassing 378,932 people. The results demonstrated that individuals genetically predisposed to napping exhibited larger total brain volume.
The research team estimated that the difference in brain volume between habitual nappers and non-nappers was equivalent to slowing down brain aging by 2.6 to 6.5 years. However, no significant difference was found between the two groups in terms of three other measures of brain health and cognitive function: hippocampal volume, reaction time, and visual processing.
Valentina Paz, the lead author and PhD candidate from the University of the Republic (Uruguay) and MRC Unit for Lifelong Health & Ageing at UCL, explained, "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."
While the study focused on individuals of white European ancestry, the authors acknowledged that the findings might not be immediately applicable to other ethnicities. Additionally, the study did not examine the specific duration of naps. However, previous research has suggested that short naps of 30 minutes or less yield the best short-term cognitive benefits, and napping earlier in the day is less likely to disrupt nighttime sleep.
The results of this study contribute to the growing body of evidence supporting the positive effects of napping on brain health. Dr. Garfield expressed hope that such findings would help reduce any remaining stigma associated with daytime napping. With nearly one-third of adults aged 65 or over reported to have a regular nap, understanding the potential benefits of napping becomes increasingly important for promoting healthy aging and preserving cognitive function.