It used to be believed that sleep was intended to rest and relax the body. It has been discovered, however, that the amount of energy saved by sleeping instead of being awake over an evening is about 50 kCal, or about the energy in a piece of toast. Instead, sleep appears to be necessary for cognitive development and health.
Sleep occurs in several stages. First, there is “light sleep”, where the body is primarily relaxing and resting as it transitions into sleep. This is followed by “true sleep”, the longest of the sleep stages (about 20 minutes). Next comes two stages of “deep sleep”; in deep sleep, many changes occur in the body, causing grogginess and disorientation if awakened. After deep sleep comes “REM” (rapid-eye movement) sleep. All dreaming occurs during REM sleep. The BBC site referenced offers a good overview of each of the stages and what their purposes appear to be.
How much sleep is enough? The answer isn’t clearly known, and is different for every person. However, it appears most people need around 7.5 to 8 hours of sleep daily. The internal body clock is designed to put us to sleep shortly after dark and wake us at first light.
Since most of us don’t get enough sleep, it is good to know how this affects us. Again, every person is different. However, many symptoms appear to be common and predictable in most people.
If a single night of sleep is inadequate, the symptoms are similar to common colds or sickness: irritability, grogginess, drowsiness, grumpiness. If a single night of sleep is missed completely, by the normal waking time the following day you will experience a return to wakefulness, but with clarity and concentration affected.
If you miss more than one night of sleep, however, the effects are more damaging. Typical effects include impairment in cognitive abilities related to language, memory, and planning. Response times decrease. Additionally, the body my experience physiological effects such as high blood pressure and a tendency towards obesity (since weight regulating hormones are released during sleep). Overall fitness can be effected, and (in men) reduced testosterone levels are common (that’s right, real men get their sleep every night). The immune system is impacted. You become more likely to develop type II diabetes. Depression, anxiety, …
If your lack of sleep is due to insomnia (rather than schedule), this is normally not self-correcting; 85% of people with insomnia still have it after 2 years.
If you’re not sleeping enough, there are only two things you can do to recoup the mental losses: get more sleep at night or take a nap. The body is naturally inclined to nap between about 2 and 4 pm every day, so if you have that option, that can be a great opportunity to make up for lost sleep at night. A 15 minute nap in the middle of the day can be nearly as valuable as one full sleep cycle (90 minutes or so) at night.
Caffeine and other drugs may help us stay awake, but they don’t give our brain the down-time it needs. Needless to say, sufficient sleep is vital to mental and physical health.
References:
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Healthy thoughts,
Jeff
