What is Sleep and Why Do We Need It?
Sleep is vital for rejuvenating both the body and the mind. Sleep is an active process that goes through several phases each night of becoming unconscious and being able to be aroused from this unconsciousness quickly.
Why Sleep?
Sleep is an overwhelming force that puts the world, and everyone in it, to bed every night. The average human being spends nearly a third of their lifespan asleep, and this has been the case throughout history. In fact, most critters in the animal kingdom exhibit some form of sleep – from fruit flies, to fish, to birds, to bears, and beyond. Yet the two simplest questions about this irresistible force, “What is it?” and “Why do we need it?”, have only begun to be addressed as insights from sleep science developed over the last century.
What is Sleep?
It is common to hear that sleep is a time when the body and mind shut down. But it’s not just a time of unconsciousness. According to The Promise of Sleep by William C. Dement, one of the founding fathers of sleep science, sleep is better defined by two things. First, it is a state when the body becomes less responsive to the outside world (you can’t see, you can’t hear, you can’t feel). Second, and most importantly, sleep is immediately reversible – for example, if someone shouts your name, you will wake up. This second point distinguishes sleep from death, coma, hibernation, anesthesia, and hypnosis.
This reversible process of sleep, when you respond less to the things around you, is not a time of complete inactivity. Brain waves, eye movements, and muscle activity all change and shift as you sleep and transition through Light sleep, Deep sleep, REM sleep, and wakefulness. Research has shown that during each of these phases, your mind is doing very different things, but it is far from inactive.
Why Do We Need It?
Sleep is a time not just for rest, but of restoration, when the body and mind recalibrate and become ready for a new day. It has been suggested that sleep is a time when memories are formed and filtered, muscles rejuvenate and grow, and the immune system builds up its defenses. The fact that sleep takes up a third of our lives indicates that these, and possibly other, processes are very important to our health and well being.
The benefits of healthy sleep are numerous. People who get enough sleep have been shown to be at lower risk for heart disease, obesity, and diabetes (although getting more or less sleep does not mean you will or will not have these problems). People who do not have sleep complaints tend to perform, look, and feel better. (For those of you who may be worried about your sleep, keep in mind that these things apply mostly to those who purposefully get less sleep than they should be getting). In the end, we need sleep because without it we would be less happy and feel worse. We want to sleep because it just plain feels good.