A simple way to sharpen cognition and memory is also an enjoyable one: Take a nap. Photo / 123RF
Even a speedy 10-minute nap can have profound effects on our cognition and mood in addition to alleviating afternoon slumps.
A simple way to sharpen your cognition and memory is also an enjoyable one: Take a nap.
Research shows that napping can not only take the edge off a night of inadequate sleep but also boost our cognitive and learning capabilities. Even a 10-minute nap can have profound effects on our cognition and mood in addition to alleviating afternoon slumps.
Even “short naps can be restorative,” said Michael Chee, the director of the Center for Sleep and Cognition at the National University of Singapore.
Taking an afternoon nap can boost mental acuity, according to a 2022 meta-analysis of 54 studies conducted by Chee, also a professor of medicine, and Ruth Leong, a postdoctoral researcher at the sleep centre.
The researchers reported the greatest benefits for vigilance and memory, but the results also showed improved mental processing speed following a siesta. Whether people habitually napped or had adequate sleep the night before, they all reaped the benefits.
In a 2023 study, Leong, Chee and their colleagues reported that napping for 10, 30 or 60 minutes improved mood and alleviated sleepiness for up to six hours after waking in a sample of 32 adults, compared with if they did not nap.
In another study, researchers found that even after chronic sleep deprivation, longer 60- or 90-minute naps can restore alertness and attention to near baseline, though research shows that catch-up sleep is still inferior to getting consistent, full nights of rest.
“The benefits of napping are basically the benefits of sleep,” said Cassie Hilditch, a sleep scientist and senior research associate with San José State University. Good sleep is the “third pillar of health,” along with diet and exercise, and allows us to regulate our biological systems and reap the benefits of exercise and diet, she said.
Like regular sleep, napping has been shown to help us encode new information and consolidate memories to make them more durable, research from Chee, Leong and their colleagues has found. Napping helped students retain information better than cramming, one 2018 study found.
Crucially, researchers have found more activation in the hippocampus, a brain area important for memory, after a nap, which may indicate restoration of its function.
Another 2023 study using a 378,932 sample from the UK Biobank reported that there was a small causal association between habitual daytime napping and larger total brain volume. However, this association was not found in the hippocampus.
Curiously, more time spent napping - and sleeping in general - is correlated with increased risk for a slew of adverse health conditions.
A 2024 meta-analysis of 44 studies found that habitual daytime napping is associated with an increased risk for cardiovascular disease, metabolic disease and all-cause mortality. However, people who napped less than 30 minutes did not have these associated risks. Napping was also associated with a decreased risk of cognitive impairment and sarcopenia, which is age-related muscle loss.
Longer naps may not be causing worse health, but instead “signal something awry in some systemic health processes” and needing to sleep more as a result, Leong said.
There is also an important distinction between planned napping and involuntary sleeping, said Chee, who is collecting data on how nap intentionality affects outcomes. Previous research suggests that more negative cognitive outcomes are associated with long, unplanned naps in older adults, while planned naps can improve memory.
Researchers stress that there are individual differences when cultivating an optimal naptime for ourselves.
“Not everyone can nap, even if they’re very tired,” said Chee, who estimated that anywhere between a third to half of people may find it difficult to fall asleep outside their normal sleep time. A recent study suggested that just closing your eyes for a few minutes can be restorative.
But for those who can nap, consider when you want to be most alert, how long you have been awake, as well as the following guidelines.
Waking up before hitting deep sleep, which occurs after about 30 minutes, can reduce the impact of sleep inertia but still reap the benefits of a nap, experts say.
Sleep inertia is the grogginess and disorientation we experience when we transition from sleep to awake. It can cause us to perform cognitively worse than if we had just stayed up all night, according to studies conducted by Hilditch and other sleep researchers.
If you have time to indulge, a 90-minute nap - which roughly coincides with the length of a full sleep cycle - may avoid waking during deep sleep while helping to recover from inadequate sleep.
“My take-home message with sleep inertia is that it can occur after any sleep episode,” she said. “So be mindful of that and not jump into some safety-critical activity immediately after waking.”
Take into account the time it takes to drift off into slumber when setting an alarm. (Time lying awake in bed is not time napping, after all.)
“You can buffer about 10 minutes to fall asleep,” Leong said.
As with night-time sleep, for your naps, too, try to keep your environment dark, cool and quiet. Use blinds or eye masks to block out excess light, which also can help improve cognition. Napping with a white-noise machine or earplugs could dampen excess noise.
Bright light - like that used in light box therapy for seasonal affective disorder - has an acute alerting effect. While most effective when used for nighttime naps, like shift workers may take, “exposing yourself to bright light can help you both feel better and perform better,” Hilditch said.
Another way of staving off sleep inertia is to use caffeine, which blocks adenosine receptors and suppresses our feelings of tiredness.
By combining a nap with caffeine, we can get sleep to rejuvenate and caffeine to fight off sleep inertia when we wake. Fortuitously, caffeine takes about 20 to 25 minutes to get into our system, which coincides with how long a short nap should be.
You can still take caffeine after waking up, though you will probably have sleep inertia for 20 minutes before it kicks in.
Consider how long you want to stay up if you take caffeine since it takes about five hours to metabolise, with individual variation, Hilditch said.
In the long term, napping is not a replacement for chronic inadequate nighttime sleep, Chee said. For those who get most of their sleep at night, napping in the afternoon lessens disruption to nocturnal shut-eye, said Leong, who notes that “many people do nap quite late” in the evening, which would affect nighttime sleep.
However, take note of when your energy levels naturally flag, and take advantage of when your body is feeling sleepy so you can be “working with your body to take that nap,” Hilditch said.
So, the next time you feel like you need a boost, rest easy knowing that a good nap can do you good.
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