There's a reason people across Spain, Greece, Italy, The Philippines, Nigeria and elsewhere have been enjoying enjoying siestas for centuries. And historians say ancient Islamic and Roman cultures started the daily afternoon nap trend long before that.
It's with good reason: A midday nap provides a quick burst of creativity, productivity and alertness.
Now, two Australian sleep experts are making the case for midday sleep once again. They say you can benefit from getting some sleep at night and some more during the day, when you start to feel sleepy again.
"Split sleep schedules may be a more natural rhythm for some people," sleep researchers Melinda Jackson of the Royal Melbourne Institute of Technology University and Siobhan Banks of University of South Australia wrote in a recent article for The Conversation. Plus, they say there's science and historical precedent to back it up.
As the hosts in the Today Show video above add, who doesn't love the afternoon snooze?
"Know it, love it, live it," said host Savannah Guthrie.
It's important to note that Jackson and Banks don't necessarily specify how long each shift of sleep should be. But, they do say that for a split sleep schedule to work, both sleep shifts need to start during a low point in your circadian rhythm (when your body wants sleep the most), and you still need to be getting an adequate total number of hours of sleep.
One study showed that split sleep can provide comparable benefits in performance as one big sleep session, if around seven to eight hours of total sleep is clocked each 24 hours.
So why sleep twice instead of all in one go?
Sleeping twice may allow more sleep
More than 35 percent of adults report getting less than the seven to nine hours of sleep that current guidelines recommend. Jackson and Banks argue sleeping in two shifts is a way that people who have trouble sleeping continuously throughout the night can clock more slumber overall.
One continuous stint of sleep may actually put undue pressure on people whose bodies are more inclined to two shifts of sleep, they wrote, "adding to the anxiety about sleep and perpetuating the problem."
There's a lot of historical evidence that humans weren't sleeping through the night for most of history, according to Jackson and Banks.
“[Sleeping twice] provides two periods of increased activity, creativity and alertness across the day, rather than having a long period where sleepiness builds up across the day and productivity wanes.”
Anthropologists have documented evidence that two-shift sleeping was the norm in preindustrial Europe and references to such sleep patterns only started to disappear from literature starting in the 17th century.
Then there's evidence daytime naps can help memory and learning. And split schedules can allow flexibility with work and family time, Jackson and Banks explained. "It provides two periods of increased activity, creativity and alertness across the day, rather than having a long period where sleepiness builds up across the day and productivity wanes," they wrote.
Other experts are not necessarily convinced
But other experts say while the strategy could be beneficial for some, more research is needed to understand how sleeping in two shifts affects the body.
One downside is waking up groggy after a second sleep, Kenneth Wright, director of the sleep and chronobiology laboratory at University of Colorado Boulder, told HuffPost.
"It poses a risk for those who have to perform immediately upon awakening, such as emergency responders and persons in the military," Wright said.
A study last year that followed sleep habits of three pre-industrial societies found that neither napping nor split sleep was common. This research suggests human sleep hasn't really changed that much over history and sleeping in one shift has long been the norm, its authors said in a press release.
“Nothing speaks against sleeping in two extended bouts (not short naps), but nothing points in the direction that this is better, either.”
More worldwide, real-world and larger studies would be needed to better understand potential benefits to recommend sleeping in two phases over one, Till Roenneberg, professor of human chronobiology at the Institute of Medical Psychology at Ludwig-Maximilian University of Munich, told HuffPost.
But if it allows someone to get more sleep overall, he said, why not try it?
If you do try it, length and timing of sleep is still important. Ideally the longer sleep bout should be at night when your circadian rhythm is telling you to sleep, and the other sleep shift should be approximately 12 hours later, he said.
Bottom line, according to Roenneberg: "Nothing speaks against sleeping in two extended bouts (not short naps), but nothing points in the direction that this is better, either."
Sarah DiGiulio is The Huffington Post’s sleep reporter. You can contact her at email@example.com.