As our lives get busier, we all find we are trying to fit more and more into what may seem like shorter and shorter days. We often make the choice to make more time by cutting back on the hours we sleep, usually underestimating the toll it’s taking on our health. Dr. William Dement of the Stanford University Center of Excellence for the Diagnosis and Treatment of Sleep Disorders, in a paper designed to educate the public about the dangers of sleep deprivation, refers to a study of one thousand people who were selected because they did not feel they were sleep-deprived and had no problem with daytime drowsiness. The shocking results of the study showed that 34 percent of these people, all claiming they had no problem with daytime drowsiness, were actually dangerously sleep-deprived.
This chronic lack of sleep is literally killing us. According to the U.S. National Sleep Foundation, sleep deprivation is associated with an increased risk of morbidity and mortality through motor vehicle accidents, obesity and related health problems, including diabetes and heart disease.
Sleep is essential to life; one of our basic necessities. On the surface, it seems simple enough—when we get tired, we just tune everything out and shut down for the night. But there is so much more to sleep than meets the eye—open or shut! It may come as a surprise to learn that sleep is not about our brains shutting down. Although humans have been sleeping since the beginning of time, it’s only been in the last few decades that we have just begun to learn that our brains and our bodies are remarkably active during this time.
Ideally, we repeatedly cycle through five phases during a good night’s sleep. Each cycle usually lasts an hour and a half to two hours. Stage 1 is a light sleep, from which we can be awakened easily. Muscle activity slows and our closed eyes move very slowly. Stage 2 is where we spend nearly 50 percent of our total sleep time. During stage 2 sleep, our body temperature decreases, eye movements stop and our brain’s electrical activity (brain waves) slows down except for occasional spurts of rapid waves. Stage 3 is deeper sleep, with no eye movement or muscle activity, extremely slow brain waves (delta waves) and sporadic bursts of smaller, faster waves. Stage 4 is the deepest sleep, with the brain producing long, slow delta waves with almost no interruptions.
During these deep sleep phases, blood pressure drops and energy is regained while essential hormones are released. Rapid eye movement (REM) sleep, which accounts for about 30 percent of our sleep time, is characterized by shallow, irregular breathing and increased blood pressure and heart rate. Our eyes twitch and dart about, yet the arms and legs are paralyzed. This is when we are dreaming. REM sleep periods and lighter sleep stages increase and the deeper sleep stages decrease in duration as the cycles progress through the night.
Recent research indicates that each of these cycles serves a different purpose. Some experts feel that REM sleep is necessary for proper memory function and solving mental conflicts. Delta wave phases are helpful for visual learning, and the shorter wave phases influence learning involving movement. Disturbing these natural rhythms of sleep can therefore result in impaired learning and memory, in addition to the physical problems we have known about for years.
We are probably all too familiar with the drowsy feelings and inability to concentrate that result from disturbed sleep. Mental acuity and physical performance suffer as a result of mild sleep deprivation. A continued lack of quality sleep can result in symptoms of mental disorders including mood swings, paranoia and hallucinations. Sleep deprivation can even trigger episodes of mania in people with bipolar disorder, as well as seizures in people with certain types of epilepsy. Research indicates that REM sleep seems to keep seizures contained to one part of the brain (instead of spreading). Sleep gives our hardworking neurons a chance to repair themselves by reenergizing and renewing overnight.
Our bodies seem to understand the role of sleep in preventing deprivation-related difficulties, as we naturally want to sleep at certain times of the day. This is due to circadian rhythms: changes that occur in our bodies (both mentally and physically) each day, controlled by a biological clock in our hypothalamus. Light signals from the retina travel to this biological clock, triggering the production or stopping production of the hormone melatonin and other bodily functions related to the sleep/wake cycle. Melatonin levels increase with darkness, resulting in drowsiness, signaling our bodies that it’s time to sleep.
We can manipulate our biological clock somewhat with external time cues (alarm clocks ringing, for example) and light therapy. This is why we can speed from time zone to time zone and, although we may suffer from the effects of jet lag, our bodies will adjust within a few days. Some people take melatonin supplements in an attempt to manipulate sleep cycles, but potential side effects of its long-term use are still unknown.
Although we can (and do!) try to meddle with nature, it is interesting that our bodies seem to be designed to follow the 24-hour cycle of daylight and darkness. The overuse of electronic devices and bright lights after what should be our bedtime disrupt both the quality and the quantity of our sleep. Each of us needs to look at and listen to both external and internal clues about when we should sleep and make a choice to follow through on those prompts to ensure that we are getting the sleep our bodies and our brains so desperately need.