What is sleep?
Sleep is the normal suspension of wakefulness. It is different from loss of consciousness, although this does occur. It is different from being sedated, anesthetized, or in a coma. It is divided into stages, including light sleep, deep sleep, and REM (rapid-eye movement sleep). Deep sleep or “quiet sleep” is considered to be the most refreshing stage, while REM sleep is sometimes also called “active sleep” and has increased brain activity and is associated with dreaming. While it is primarily regulated by the brain, the entire body is involved in the sleep process. Therefore, disorders of sleep cause dysfunction and illness in other parts of the body (i.e., high blood pressure, obesity, and diabetes).
How much sleep is enough sleep?
Everyone requires an average of five hours of sleep per night, which is known as “core sleep.” Some people may require less, and some may require more. The better question is how much sleep I need. You know you are getting enough sleep, when you wake up feeling refreshed, have good alertness and cognition during the day, and do not again feel sleepy until bedtime. You feel like you are at your best. A good way to gauge how much time this is to sleep for several days without a strict bed or wake time and no pressure to be awake for anything (i.e., several vacation days where you truly have no desires or obligations to be anywhere).
It is probably not a coincidence that one period of sleep and one period of wake together adds up to 24 hours. If you add up the sleep-wake cycle (i.e., time asleep and time awake), you would find that one complete cycle usually lasts 24 hours, which is the time it takes the earth to spin one time on its axis (i.e., one day and one night). This natural rhythm of alternating sleep and wake is referred to as our circadian rhythm. Interestingly, even people who are blind can be affected by changes in their light-dark schedule, which is thought to affect people on more than just a visual level.
What if I don’t get enough sleep?
You can be sleep deprived of all stages of sleep or can be sleep deprived of a particular stage of sleep. For example, if you take benzodiazepines as sleeping aids or for anxiety, you will suppress your slow wave (deep sleep). A lack of slow wave sleep will make you feel unrested, achy, and tired. If instead you take tricyclic antidepressants, amphetamines, barbiturates, or alcohol, you can suppress your REM sleep (dreaming sleep). A lack of REM sleep can impair your learning and concentration. Sleep can also be disrupted by stimulants, such as nicotine or caffeine.
Total sleep deprivation can kill a lab rat in about two weeks, the number is likely lower for humans. However, partial sleep deprivation (getting 1-2 hrs. less than necessary per night) can go on for months or years. It can also lead to increased health problems and premature death. One sign that you may not be getting enough sleep is if you sleep longer (ie, “sleep in”) on weekends or vacations.
One of the most common reasons for people not to get enough sleep is that they stay up late watching television or working or playing on the computer. Not only is this causing them to deprive the body of necessary rest, but this promotes insomnia by exposing oneself to late evening light. Before the invention of electricity, light exposure at night was minimal and usually limited to low illumination candlelight.
What if I get too much sleep?
Just as too little sleep can be damaging, too much sleep can be equally bad. Increased time in bed has been linked not only to depression, but also to increased mortality. Time in bed should generally be limited to less than 10-12 hours (with some exception in the adolescent years), and time spent lying awake in bed should be limited to less than 15 minutes.
There are several serious sleep disorders which are associated with consistent daily sleep times of greater than ten hours. Some of these disorders are linked to excessive eating, depression, and head trauma and brain tumors. One more common disorder is African Sleeping Sickness. This disorder is transmitted to humans by the bite of the tsetse fly. It can initially cause headaches and joint pain, then it attacks the central nervous system, where it leads to confusion, disruption of the sleep cycle (reversal of night or day and loss of REM) and death. It can be treated with medications.
Can I control how much sleep I get?
The opportunity for sleep and meeting your total necessary sleep time is entirely up to you. Lifestyle and work choices may affect the timing of sleep, but frequently people will trade sleep time for other preferable activities (i.e., watching television, reading, socializing) at the expense of their sleep time.
Am I legally obligated to sleep?
Interestingly, in some states that answer to this question is yes. Driving without enough sleep has been recognized as a cause of impairment and in some states is the equivalent of driving drunk. Driving precautions are often recommended for those with sleep disorders, and prior to treatment, some people may be placed on temporary medical disability until their sleep disorder can be treated (i.e., airline pilots, bus drivers, et cetera). Some of the commonly used driving precautions are as follows: do not drive when you are sleepy, take frequent breaks on long trips, nap for 15 min when sleepy before driving, pull over if you have signs of sleepiness while driving (i.e., crossing lines, automatic behaviors (driving on autopilot), stopping short, et cetera), and being especially careful when driving home from work or early in the morning.
It only takes 5-10 seconds of inattention at the wheel for a moving vehicle to cause a fatal accident. For those who are at high risk for falling asleep at the wheel, prescription stimulants can be used to promote wakefulness or vigilance testing can help assess their risk.