This episode of SciShow is supported by NordVPN.

Head over to nordVPN.com/SciShow to learn more about virtual private networks and internet security. [ ♪INTRO ]. Between 50 million and 70 million Americans are thought to have some sort of sleep disorder.

If you're one of them, you're probably desperate for a good night's rest. And if you want to sleep better, science may have an option for you — one as old as nursery rhymes. Humans have rocked their infants to sleep since well before the advent of ergonomic carriers and Instagrammable gliders, and a pair of 2019 studies suggest that grownups could stand to benefit too.

In the first study, 18 healthy young adults spent one night in a bed that gently rocked 10 centimeters from side to side every four seconds, and one night in a stationary bed. Researchers measured the subjects' brain activity and found that while rocking, the young adults reached the second stage of non-REM sleep, the stage that comes right before our deepest and most restful sleep, in an average of 10 minutes. That's compared to over 16 minutes when the bed wasn't in motion — in other words, they fell asleep faster.

The subjects didn't sleep longer while rocking, but they did spend longer periods in the third stage of non-REM sleep, which is that deep and restful stage, and they also woke up less often. Falling asleep faster and sleeping more deeply weren't the only observed benefits. Participants recalled word pairings that they learned the night before with greater accuracy, which suggests that rocking might improve memory.

The memory boost seems to be tied to an increase in what are known as sleep spindles. These are part of an EEG pattern that your brainwaves make during non-REM sleep. A 2011 study showed that rocking during a short nap led to sustained spindle activity, but the new study in young adults was the first to show a similar effect with continuous rocking through the whole night.

The second study focused not on humans but on mice which were kept in cages that gently moved from side to side at night. And they, too, fell asleep faster and remained asleep longer, though they didn't sleep more deeply like their human counterparts. Importantly, the mouse study offered insight into why rocking improves sleep.

It all seems to have something to do with the vestibular system, which gives us our sense of balance and spatial orientation. The researchers repeated their experiment using mice that lacked a specific bit of the organs in the inner ear that allow vertebrates to sense movement. And this time, the mice didn't benefit from rocking, suggesting that that particular sensory system was vital for rocking to have any benefit.

You might not want to shell out a few grand for a rocking bed just yet, which are a thing by the way. The first study's sample size of 18 young adults was small, and they only slept in the rocking beds for one night, so we don't know how broadly these results will apply. But these studies do open up new research questions, and a surprising potential treatment option for insomnia, mood disorders, and maybe even memory impairment.

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