If you believe the evolutionary theory of sleep, you might
be wondering why humans, not just non-human animals, still do it. There are
famous examples of people being able to live on just a fraction of the sleep
the rest of us have. For example, ex-British prime minister Margaret Thatcher
was thought to have as little as 4 hours of sleep during her leadership of the
country, and Thomas Edison, creator of the modern light bulb, spent long periods
awake with limited effects.
Such cases are rare, though, and research has shown that
sleep is important, and that sleep deprivation can have serious side-effects.
Take the case of American DJ Peter Tripp, who in a radio stunt, spent eight
days without sleep. During this time, Tripp experienced hallucinations and delusions
whilst awake, and he is thought to have experienced longer term effects. After
the experiment, the DJ caught up on only some of the missed sleep, but it should
be pointed out that the non-laboratory conditions of the test and potential
genetic factors relating to the side-effects mean that we can't say this would
happen to everyone deprived of sleep.
Another case, this time of Randy Gardner, was studied by
psychologist Thorne in 1998. Gardner spent a staggering 11 days without sleep,
but despite experiencing vision and speech problems during that time, he appeared
to recover better than Peter Tripp, even though he caught up on just 25% (15
hours) of the sleep he missed.
The different stages of sleep are thought to be of varied
importance. REM sleep - the period in which our eyes move rapidly from side-to-side
and dreaming occurs - and stage 4 are more important than the rest of sleep,
known as NREM or non-REM sleep.
The studies into sleep deprivation clearly show that even
humans can suffer serious side effects from the lack of it. A pointer to sleep's
importance is babies' sleep patterns. Babies spend upto three times the amount
of time asleep that adults do, and spend as much as 8 hours in REM sleep, indicating
that such a vital stage in a person's development requires much more sleep than
the rest of our lives.