Rocking allows for better sleep – even in insomniac adults!

By Dr. Ananya Mandal, MDJun 21 2011

A new study shows that people tend to sleep faster and even achieve better quality sleep if they are gently swayed. The findings may explain why parents instinctively rock babies to sleep, and why we find it so easy to nod off when slumped in a rocking chair, they add

In tests, 12 men who described themselves as 'good sleepers' were asked to have sleep in a hammock. Each took two 45-minute naps, first when it was swinging and then again when it was still. On both occasions, they were left in a dark and quiet room while their brain activity was monitored.

All the volunteers fell asleep more quickly when they were being rocked, the scientists found. “We observed a faster transition to sleep in each and every subject in the swinging condition,” said researcher Dr Michel Muhlethaler, from the University of Geneva. Rocking also changed the nature of their sleep, his team reports in the journal Current Biology.

“It is a common belief that rocking induces sleep: we irresistibly fall asleep in a rocking chair and, since immemorial times, we cradle our babies to sleep,” said Dr Sophie Schwartz, from the University of Geneva in Switzerland. “Yet, how this works had remained a mystery. The goal of our study was twofold: to test whether rocking does indeed soothe sleep, and to understand how this might work at the brain level.”

During a typical night, people go through four distinct stages of sleep. First is N1, the transition between wakefulness and sleep, which lasts for five to ten minutes. It is followed by N2, which takes up half of a night's sleep. The body's temperature then drops before it enters N3, a deep sleep lasting for around 30 minutes. The brain moves between the second and third stages of sleep several times before it begins rapid eye movement, or REM. Typically starting around 90 minutes after falling asleep, REM is the stage in which one dreams.

Rocking increased the amount of time spent in a dreamless stage called N2, which takes place soon after one falls asleep. The action also encouraged bursts of brainwave activity called sleep spindles. This is normally a sign that the deeper stage of sleep has been reached and allows the brain to consolidate memories from the day.

The researchers are now planning to investigate whether rocking improves longer periods of sleep or could help treat disorders such as insomnia. Future tests could also explore whether it encourages the brain to repair itself after injuries.