To uncover this link, the researchers selected data from the UK Biobank (which has inputs from nearly 379,000 people) and identified people who had particular snippets of DNA that are known to predispose a person to regular naps. (Using genetics, they were able to avoid the problem of confounding lifestyle factors that could affect the connection between napping and cognition.) They then analyzed brain data from the Biobank pool (including brain MRIs) from people who had the nap genes compared to those who didn’t, and found that people predetermined to nap had significantly larger brains.
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Napping May Provide Defense Against Neurodegeneration
This connection between habitual napping and brain size represents a key finding because brain volume shrinks as we age, affecting memory performance and cognitive function (and that process occurs at a faster rate in people with cognitive decline or neurodegenerative disease). “Based on our findings, we hypothesize that regular napping provides some protection against neurodegeneration by compensating for lack of sleep,” says study lead author and PhD candidate Valentina Paz, MSc, a researcher at the University of the Republic of Uruguay and University College London.
“We hypothesize that regular napping provides some protection against neurodegeneration by compensating for lack of sleep.” —Valentina Paz, MSc, researcher at the University of the Republic, Uruguay
More broadly, this finding suggests that taking regular naps may help us better retain our brain size as we age and prevent cognitive decline as a result. “Brain volume measurements have been used as markers of neurodegeneration, so that a greater brain volume implies less degeneration,” says Paz. “Understanding this difference in brain size (in people who nap versus those who don’t) has important clinical implications for mitigating age-related cognitive declines.”
Interestingly, Paz and her co-investigators did No find a similar link between a person’s genetic likelihood to nap regularly and other elements of brain health, such as the size of the hippocampus (an important area for memory), reaction time, and visual memory.
For that reason, Paz says the link between frequent daytime naps and brain health is still unraveling. It is also important to note that this study did not take into account factors such as the presence of sleep inertia, the quality of the previous sleep period, or the duration and timing of naps, all of which could influence whether a nap has a positive, negative, or no effect on cognition.
However, with regard to brain volume, it is worth reiterating that this finding is significant. Taking into account the typical rate at which we tend to lose brain volume with age, the study researchers were able to calculate that the difference they identified in brain volume between regular nappers and non-nappers was equivalent to about 2.6 to 6.5 years of aging. “This difference is roughly equivalent to the difference in brain volume observed between individuals with normal cognitive function and those with mild cognitive impairment,” says Paz.
Such a potential brain boost from napping matches previous research indicating that napping can improve certain elements of cognition, particularly in people who are learning new information, says neurologist Brian Murray, MD. “There’s something about sleep that helps consolidate and organize the brain,” he says.
How to Optimize Your Naps for Cognitive Health
In the spirit of boosting the beneficial effects of daytime rest on the brain, Paz says it’s important to consider not only that your nap but as your nap
In general, it is better not to overdo it. Paz advises a short nap of five to 15 minutes (and no more than 30 minutes maximum) in length; This way, you won’t risk plunging into the deeper stages of sleep, from which it will be more difficult to wake up.
It’s also smart to take a nap sometime in the afternoon, Paz says, ideally around 2 or 3 p.m. (if you normally go to bed around 10 or 11 p.m.). Previous research has found this “post-lunch dip period” to be the optimal time to nap, Paz says, to overcome the all-too-common dip in alertness and performance around noon. Also, avoiding a nap too late in the day ensures that you won’t spend some of your sleep boost and possibly interfere with your ability to fall asleep that night.
For the best quality nap, Paz prescribes a comfortable environment in which light, temperature and noise are taken into account. In particular, it is best to choose a quiet, cool, and dark room for naps; If your space is noisy, you can turn on some white noise to mask outside sounds, and if it’s bright, try putting on an eye mask for the dark.
More details on how to achieve the ideal nap for health purposes will require further research, Paz says. But in the meantime, the new study represents a big step forward in linking habitual napping to increased total brain volume, and in turn, a healthier brain. “With different data sets and methodologies, we will continue to investigate the association between napping and general health,” says Paz, who is determined to shed more light on the “grey area” of our gray matter.
