June 20, 2023 – A person’s brain gradually shrinks with age, but a new study suggests that people who regularly take short, daytime naps may thwart that aging process by the equivalent of 2 to 6 years.
The researchers wrote that “this difference approximately equates to the difference in brain volume between people with normal cognitive function and mild cognitive impairment.”
Published Monday in the journal Sleep Health, the study looked at data for 378,932 people ranging in age from 40 to 69 years old. The average age was 57. The people, all from the United Kingdom, had previously contributed their health and genetic information to a database called the UK Biobank.
Starting at 35 years old, the brain begins to shrink at a rate of 0.2% per year, and the rate increases to 0.5% per year at age 60, the authors noted. They chose to examine the impact of napping on brain volume because the rate that the brain shrinks has been linked to disorders like Alzheimer’s disease, and brain volume has been linked to sleep disorders like insomnia.
“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 University College London genetic epidemiology researcher Victoria Garfield, PhD, in a statement.
The researchers used a complex method based on a person’s genetic profile to identify people who habitually took daytime naps. As part of their participation in providing data to the UK Biobank, the people in the study had taken cognitive assessments to evaluate their visual memory and their reaction time. A group of people in the study also had brain images from MRIs on file in the UK Biobank, which the researchers used to analyze the size of the people’s brains.
The authors noted that previous research has shown that daytime napping among older people impacts brain health, such as boosting performance on cognitive tasks. Some studies have shown the benefits of napping to persist for hours or even an entire day. However, this latest study did not find a link between napping and people’s performance on visual memory and reaction time tests. The researchers wrote that they were surprised by this finding and suggested that the tests the study participants took may have been flawed.
“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,” Garfield said.