The popular lullaby “Rock-a-bye Baby” attests to the fact that a gentle rocking motion is often the key to coaxing a crying infant to sleep. But as Ed Cara writes for Gizmodo, two related surveys of young adults and mice suggest rocking’s benefits aren’t limited to the young.
In fact, a team of Swiss researchers report in the latest issue of Current Biology, human participants asked to drift off in a rocking bed not only fell asleep faster, but also spent more time in deep sleep and exhibited improved memory skills. Although mice included in a separate Current Biology study fell asleep more quickly than their non-rocking counterparts and enjoyed increased overall sleep time, rocking did not appear to yield similar levels of higher sleep quality for the rodents, according to BBC News’ Laurel Ives.
The human-centric study, led by Laurence Bayer and Sophie Schwartz of the University of Geneva, involved 18 men and women with an average age of 23. None had previously recorded sleep problems.
Participants spent a total of three nights sleeping in the laboratory, Michael Le Page notes for New Scientist. The first was designed to acquaint subjects with their unusual resting environment, while the remaining two were split between a rocking bed, which gently swung 10 centimeters every four seconds, and an identical yet stationary bed.
As participants slept, the scientists tracked their brain waves via electroencephalography (EEG) recordings. These readings revealed that individuals in gently rocking beds transitioned to “real” sleep more quickly, spent more time in stage three of non-rapid eye movement (REM), or “deep” sleep, and experienced fewer sleep disruptions. They did not, however, sleep longer on average than those in non-moving beds.
According to the Guardian’s Nicola Davis, the researchers also found that being rocked improved subjects’ recall ability. Participants tasked with memorizing unrelated pairs of French words were tested before and after each night; those who slept in rocking beds made fewer mistakes and remembered pairings with greater accuracy.
It’s likely that these heightened memory skills stem directly from higher-quality sleep. As Cara explains for Gizmodo, one of the main purposes of sleep is memory consolidation, or the process of stabilizing and retaining memories after initial acquisition. For Scientific American, Bret Stetka further points out that rocking better synchronized non-REM sleep brain waves in the thalamocortical network, which is linked to both sleep and the storage of long-term memories.
The second sleep study, led by Paul Franken of the University of Lausanne, found that mice housed in rocking cages fell asleep faster and slept longer overall. They did not, however, experience increased sleep quality. The mice’s ideal rocking rate, according to the study, was four times faster than that of human participants.
Cosmos’ Samantha Page writes that mice lacking functional otolithic organs—elements of the vestibular system, which is responsible for balance and spatial orientation—did not benefit from rocking. As Page summarizes, “If you cannot sense that you are rocking, the rocking does not help lull you to sleep. At least, if you are a mouse.”
Together, the studies could have significant implications for insomniacs and really anyone hoping to get a good night’s sleep.
In an interview with Science News’ Laura Sanders, Laurence Bayer, a co-author of both new surveys, concludes, “If rocking can help this population to sleep better, it will be a nice alternative or a natural complement [to sleeping pills].”