Why Does Gentle Lateral Bed Rocking Enhance Sleep?
It is common knowledge that sensory inputs influence sleep. Most people for example have trouble sleeping when there is loud traffic noise (auditory inputs), while many people report sleeping well when listening to the sound of the rain. Olfactory sensory inputs, scents, can positively or negatively affect sleep. Bright light overstimulating the visual senses has deleterious effects on sleep, while darkness promotes it.
Most people sleep well in a moving motor or train car, as the movements stimulate the vestibular system which is located in our inner ear. The vestibular system detects motion and spatial orientation and provides this information to the brain.
Babies have been rocked to sleep in their moms’ arms since the dawn of humanity. Hammocks may have been used as baby (and adult) cradles by ancient civilizations. Wooden rocking cradles were first patented in the mid 1800’s although it’s likely that they were around in some shape or form long before that. Finally the first powered rocking baby cradle was invented in 1924, right around the time when half of American households had electricity.
Science confirms what has been common knowledge for thousands of years. Rocking motion helps people get to sleep faster and remain in the most recuperative deep sleep for longer. In a recent scientific study, sleep researchers showed that a lateral (side to side) rocking motion of the bed at 0.25 Hz (once every 4 seconds) reduced the time it took human subjects to fall asleep. It also increased the time spent in the deepest and most important NREM 3 sleep phase. Human subjects rocked while sleeping performed significantly better at learning tasks than those who were not rocked.
Animal experiments on mice strongly suggest it is the stimulation of the vestibular system that leads to improved sleep when laterally rocked. Like humans, mice sleep better when gently rocked. The effect can be switched off in mice when certain genes responsible for the vestibular system are shut off.
Pleasant sounds, smells, dark lighting and gentle rocking movement all promote sleep as they offer sensory stimulation signalling to the brain that it’s time to fall asleep and stay asleep.
Under normal conditions most people take up to 20 minutes to fall asleep. Deep sleep (NREM 3) may be interrupted by reverting into medium sleep (NREM 2).
Experiments by sleep researchers on human subjects have shown that when being rocked, the time it takes to fall asleep is shortened,. Recuperative deep sleep (NREM 3) is longer. Among other benefits, learning is improved as a result.
