Many people who nap often say that after a quick snooze, they feel sharper and more alert and see a boost in their mood. Plus, a nap is more effective than caffeine for overcoming that midafternoon dip in energy a lot of individuals experience.
However, these benefits are elusive for others. If you’re not a habitual napper, you may find yourself groggy after waking from a nap and dragging for the rest of the day.
It’s tough to say why the napping experience differs for each person. And that’s why researchers decided to dig into how our genes may impact our likelihood to nap.
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Genetics, napping and brain volume
A study led by Harvard University identified several genetic variants involved in napping by collecting data on almost half a million UK Biobank participants. But recently, an international team of researchers decided to take this data a step further and establish whether there is a causal relationship between daytime napping and specific measures of brain health.
They analyzed health and cognition outcomes for people aged 40 to 69 with the previously identified genetic variants, as well as several different subsets of these variants. They adjusted them for any potential bias, for instance avoiding variants linked to excessive daytime sleepiness.
They used Mendelian randomization to examine 97 snippets of DNA believed to show people’s likelihood of habitual napping. Then, they compared measures of brain health and cognition in people who are more genetically predisposed to nap with people who did not have these genetic variants.
“By looking at genes set at birth, Mendelian randomization avoids confounding factors occurring throughout life that may influence associations between napping and health outcomes,” says lead author and Ph.D. candidate Valentina Paz of the University of the Republic in Uruguay and MRC Unit for Lifelong Health & Ageing at University College London (UCL).
What the researchers found was fascinating. Overall, people who are genetically “programmed” to nap had a larger total brain volume than those who aren’t. They estimated the average difference in brain volume between the two was equivalent to 2.6 to 6.5 years of aging.
In other words, daytime napping may help significantly slow the rate at which our brains shrink as we age. This is great news, as larger total brain volume is linked to a lower risk of dementia and other diseases.
The researchers did not obtain any data on nap duration. But earlier studies suggest naps of 30 minutes or less provide the best short-term cognitive benefits.
The researchers did note that they did not find a difference in how well those predisposed to be habitual nappers did in terms of hippocampal volume, reaction time and visual processing, all of which are additional markers of brain health and cognitive function.
Still, senior author Dr. Victoria Garfield of the MRC Unit for Lifelong Health & Ageing at UCL says the findings “suggest that, for some people, short daytime naps could help preserve the health of the brain as people age.
“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 adds.
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Keep it short and sweet
Now, you may have heard that frequent daytime napping is connected with cardiovascular disease, hypertension, stroke, diabetes, Alzheimer’s disease and death. However, there was one thing that these studies had in common: the naps in question tended to be 60 minutes or longer.
Some experts believe the point where napping becomes problematic is in the zone between 30 minutes and 1.5 hours. At this point, the body can drop into a deep sleep, but it doesn’t have the chance to complete a full sleep cycle. This could be why some nappers feel groggy upon waking.
Also, napping may be a symptom, not a cause, of the health problems mentioned above. If someone is experiencing a constant sleep deficit and persistent state of exhaustion that leads them to sleep during the day, it could be a sign of an existing, underlying health issue.
So, if you’re looking to get the brain benefits of napping but avoid the risks, the sweet spot appears to be between 20 and 30 minutes in the middle of the day. This gives you just enough time to get some light rest without slipping into the heavier sleep that can be difficult to rouse yourself from. And if you nap before 3 p.m., it reduces the likelihood of the nap impacting your nighttime sleep.
Sources:
Regular napping linked to larger brain volume — EurekAlert!
Is there an association between daytime napping, cognitive function, and brain volume? A Mendelian randomization study in the UK Biobank — Sleep Health
29 Napping Statistics & Facts to Boost Your Energy Levels — DisturbMeNot!
The science of naps — American Psychological Association
Who’s Napping, How Long, and What Does It Mean for Our Health? — Sleep Foundation