July 26, 2023
Feeling guilty about taking that afternoon nap? Don’t be. Napping may be good for the brain, according to a new report.
The study, from researchers at University College London and the University of the Republic in Uruguay, found that regular napping may slow the rate at which the brain shrinks as we age. A larger brain volume is associated with better memory and thinking skills and a lower risk of developing Alzheimer’s disease.
For the study, published in the journal Sleep Health, researchers analyzed medical data from 378,932 men and women who were part of the UK Biobank, a large and ongoing health study of people in Britain. They ranged in age from 40 to 69.
The researchers used a technique called Mendelian randomization that helps to pinpoint the cause of a specific health outcome, in this case the effects of napping on the brain. They identified 97 snippets of DNA that predispose people to be “daytime nappers,” who regularly take an afternoon nap. Using MRI brain scans, they compared the brains of many of the nappers to those of their peers who did not have a genetic tendency to nap.
They found that, overall, people who were predisposed to nap had a larger total brain volume. The nappers’ brains were, essentially, 2.6 to 6.5 years “younger” than the brains of their peers who didn’t regularly take naps, the research team estimated. Although participants prone to naps did not perform differently than non-nappers in tests of visual memory and reaction time, it is important to note that this study did directly look at the effect of taking a nap on these measures.
“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 Dr. Victoria Garfield of University College 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.”
The findings build on earlier research showing that sound, restorative sleep, including naps, can be good for the brain. About a third of older adults nap regularly, and in some cultures, napping is normal and happens daily. Naps lasting from 30 to 90 minutes have been tied to improvements in mood, alertness and performance on cognitive tasks.
But excessive napping, longer than 90 minutes at a stretch or at multiple times during the day, or suddenly finding yourself napping when you didn’t used to take naps, may be a sign of a more serious problem. Older adults who nap excessively are at increased risk of developing Alzheimer’s disease, studies suggest, and people in the early stages of Alzheimer’s often nap excessively. Feeling excessively tired during the day may also be a sign of poor nighttime sleep quality or a health problem like sleep apnea, which interrupts breathing and causes people to wake up hundreds of times during the night.
Ultimately, it may be best to aim for a sound night’s sleep, and if you’re a napper, to go ahead and indulge in that afternoon siesta. Healthy older adults who sleep soundly tend to have less buildup in the brain of beta-amyloid, the toxic protein that is a hallmark of Alzheimer’s disease. Deep sleep appears to act as a kind of cleaning system, ridding the brain of toxic debris. Until more effective treatments or a cure for Alzheimer’s disease are found, getting better quality sleep may be one more way to help slow the onset of dementia as the years advance.
By ALZinfo.org, The Alzheimer’s Information Site. Reviewed by Eric Schmidt, Ph.D., Fisher Center for Alzheimer’s Research Foundation at The Rockefeller University.
Source: Valentina Paz, MSc; Hassan S. Dashti, PhD; Victoria Garfield, PhD; et al: “Is there an association between daytime napping, cognitive function and brain volume? A Mendelian randomisation study in the UK Biobank.” Sleep Health, June 19, 2023