Short afternoon naps help protect against dementia
According to new research, short naps may keep the brain healthy as we age. A short-term dose of sleep may slow brain shrinkage, which occurs faster in people with neurodegenerative diseases.
Short naps may help protect brain health with age, researchers suggested, finding that this practice appears to be related to an increase in brain volume.
While previous research has suggested that prolonged sleep may be an early symptom of Alzheimer's, other work has shown that short sleep can improve people's ability to to learning.
Now the researchers say they have found evidence that daytime naps may help protect against brain shrinkage.
The team says this is of interest because brain shrinkage, a process that occurs with age, accelerates in people with cognitive problems and neurodegenerative diseases, and some research suggests that this may be due to sleep problems.
“According to these studies, we found an association between habitual daytime sleep and an increase in total brain volume, which may indicate that regular daytime sleep provides some protection against neurodegeneration by compensating for poor sleep,” – researchers note.
In an article published in the journal Sleep Health, researchers at UCLA and the University of the Republic of Uruguay report that they used data from a British Biobank study that collected genetic, lifestyle and health information from 500,000 people. between the ages of 40 and 69 when applying for a job.
The team used data from 35,080 Biobank participants to find out if a combination of genetic variants that had previously been associated with self-reported daytime sleep habits , also with brain size, cognition and other aspects of brain health.
Given that these options are set at birth and are assumed to be randomly distributed, the approach allows researchers to investigate the effects of daytime sleep on the brain by reducing the influence of lifestyle factors that can affect people's sleep habits and brain health, such as smoking or physical activity. .
“This is like a natural randomized control trial,– said Dr Victoria Garfield, co-author of the study at University College London, adding that the variants were fairly common. – They are present in about 1% of the population, which is actually quite a lot”.
Indeed, although at first it seemed that participants who reported never or rarely slept during the day had a larger total brain volume, the team found an inverse relationship when looking at genetic predisposition to sleep, suggesting that the original finding may have been due to other factors skewing the relationship between daily sleep intake and brain size.
Overall, the team found an association between genetic predisposition to habitual daytime sleep and an increase in brain volume, equivalent to a reduction in life expectancy of 2.6-6.5 years, although there was no association with cognitive measures such as reaction time.
“Maybe short naps…may help preserve brain volume, and that’s a positive thing, potentially [for] dementia prevention,” – says Victoria Garfield, adding that previous studies have shown up to 30 minutes of sleep can be beneficial.
Dr. Garfield noted that there are many risk factors that can lead to dementia, while many others factors can also affect brain volume.
Moreover, the study is based on white British data only, and the exact length of daytime sleep associated with benefit is unclear. It is also unclear whether the same benefits of daytime sleep will be seen in people without a predisposition, writes The Guardian.
Professor Tara Spiers-Jones, President of the British Neurological Association, Team Leader at the British Dementia Research Institute and Associate Director of the Discovery Centre. in Brain Science at the University of Edinburgh, welcomed the study, although she said it has limitations, including the British self-reported nap habit. «This study is important because it adds to the evidence that sleep is important for brain health,» – she said.