Why We SleepScientists have yet to determine exactly why people
sleep. However, they do know that humans must sleep and, in fact,
people can survive longer without food than without sleep. And people
are not alone in this need – all mammals, Scientists have proposed the following theories on why humans require sleep:
For many small mammals such as rodents, sleep has other particular benefits, as it provides the only real opportunity for physical rest, and confines the animal to the thermal insulation of a nest. In these respects sleep conserves much energy in such mammals, particularly as sleep can also develop into a torpor, whereby metabolic rate drops significantly for a few hours during the sleep period. On the other hand, humans can usually rest and relax quite adequately during wakefulness, and there is only a modest further energy saving to be gained by sleeping. We do not enter torpor, and the fall in metabolic rate for a human adult sleeping rather lying resting but awake, is only about 5-10%. More than 20% of Americans are shift workers who work and sleep against their bodies’ natural sleep-wake cycle. While a person’s circadian rhythm can not be ignored or reprogrammed, the cycle can be altered by the timing of things such as naps, exercise, bedtime, travel to a different time zone and exposure to light. The more stable and consistent the cycle is, the better the person sleeps. Disruption of circadian rhythms has even been found to cause mania in people with bipolar disorder. "Sleepiness" cannot easily be quantified although such tests can be useful in getting some grip on it. Four common tests are used to measure and quantify effects of stimulants and symptoms of disorders.
The two-phase model provides some guidance as to why people get sleepy – duration of prior waking and place in the circadian cycle. Sloth as a sin
The "seven deadly sins" formulated by the mideaval monks included Sloth. The Bible in Proverbs 6:9 includes the line: "How long will you sleep, O sluggard? When will you arise out of your sleep?" But a more nuanced understanding of sloth sees it as a disinclination to labor or work. This isn't the same as the desire for healthy sleep. On the contrary, a person can't do work without rest periods and no one can operate at top performance without adequate sleep. The Puritan work ethic can be adhered to and respect still paid to the sleep needs of healthy humans. It is wrong to see sleep as a shameful activity. Future Scientific Research into Sleep
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Sleep Disorders
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Orexin Antagonists in the Spotlight
"O Sleep, rest of all things, mildest of the gods, balm of the soul..." (Iris to Hypnos. Ovid, Metamorphoses) |