The Science of Sleep

Despite years of research, advances in medicine, and the possibility of a cure for cancer within the next decade, we still don’t know the exact function of what we spend one-third of our lives doing: sleeping. National Geographic quotes William Dement, cofounder of the Stanford Sleep Medicine Center, on the mystery of why we sleep: “As far as I know, the only reason we need to sleep that is really, really solid is because we get sleepy.” Why we sleep seems to remain a timeless question—yet we know that sleep is crucial to our well-being, and its quality determines our lives.

Sleep, it seems, is more than just a period of rest. For instance, hibernating animals must actually catch up on sleep after coming out of hibernation, a process known as rebound sleep. Even though they’re emerging from a deep state of lowered metabolism, they still need sleep to survive, which suggests that sleep serves a function other than just energy conservation. Another fun fact: Newborn babies spend up to nine hours a day in REM sleep, the stage of the sleep cycle where dreams mostly occur, whereas the average adult spends less than two hours in REM.

How we are affected by sleep is also of particular interest to researchers. There’s no question that we feel better after a good night’s rest. Proper sleep contributes to psychological health and well-being. However, most of us will encounter sleep disturbances throughout the course of our lives. In fact, one out of three people will experience insomnia at some point in their life.

A mere week of unrest or sleep deprivation can cause severe changes in mood: depression, decreases in emotional regulation, and obvious depletion. It seems that a good night’s rest can also enhance the positive feelings and states of being that we cultivate through yoga practice. There’s really something to the idea of “sleeping off” difficult experiences.

Something else we know about sleep: Yoga can help improve it. Sleep is a function of the parasympathetic nervous system, the system devoted to rest and digestion. Not surprisingly, sleep onset (the natural oncoming of sleep) and yoga are both associated with an increase in parasympathetic activity. In addition, meditation techniques that don’t require intense mental effort or concentration, such as yoga nidra, open-awareness methods, and self-hypnosis, have all been shown to increase parasympathetic dominance.

So can yoga play a role in our sleep patterns? Can it relieve sleep disorders such as insomnia? Research seems to say yes. In one study on yoga and sleep, participants practiced a 45-minute Kundalini Yoga sequence before bedtime that included long, slow breathing and meditation. The results showed statistically significant improvements in sleep efficiency, total sleep time, and how long it took to fall asleep. Another study showed that young adults who practiced Bikram Yoga regularly woke up fewer times in the night, a sign of better sleep quality.

The Charaka Samhita, a foundational Ayurvedic text, states, “Happiness, misery, nourishment, emaciation, strength, weakness, virility, sterility, knowledge, ignorance, life and death—all these occur depending on proper or improper sleep.” It seems that, if we want to live to our full potential, we must approach sleep as a personal practice.

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