For as long as anyone can remember, parents have rocked their babies to sleep. A study from the University of Geneva offers some clues on why this works so well, and why it's not just good for babies. It seems to work just as well with adults.
Rockers also showed more sleep spindles, intense bursts of brain activity that last about a second and are indicative of deep sleep that is more refreshing.
Using a bed that could be set to rock gently or remain stationary, the researchers found that adults fell asleep faster when the bed was rocking.
Once the volunteers were asleep, rocking increased the duration of N2 sleep, a stage of non-rapid eye movement sleep that makes up about half of a good night's sleep. Rockers also showed more sleep spindles, intense bursts of brain activity that last about a second and are indicative of deep sleep that is more refreshing. Research has shown that the quality of sleep is the key to its restorative power.
The study was of 12 male volunteers, age 22-38, who had no history of sleep problems and neither napped nor reported being tired during the day. Each took two, 45-minute afternoon naps, one with the bed stationary and one while it was swinging gently. While they napped, their brain activity was monitored by electroencephalogram (EEG). The two sessions were at least one week apart.
The swinging bed was constructed by suspending a bed from four metal rods that also connected to the bed frame. This allowed the bed to hang in the air. A silent electric motor was then attached to the bed. When turned on, the motor would swing the bed gently back and forth. The researchers liken this to an experimental hammock.
Of the ten volunteers who completed the study, eight found the bed more pleasant while it was swinging, while only one found it more pleasant when stationary. The other volunteer found both conditions equally pleasant.
The researchers say that the next step is to find out whether rocking works for periods of sleep longer than 45 minutes and also to see if it's helpful for people with sleep disorders like insomnia.
The rocking study appears in the June 21, 2011 issue of Current Biology.