Thank you for the thought-provoking question! Here's what I found in my research: People spend more time sleeping than doing anything else! A
summary of sleep theories is as follows:
* Sleep helps the body save and restore energy by slowing down the metabolism, which conserves energy.
* Sleep may help replenish our stores of neurotransmitters because most neural activity decreases during sleep.
* Slow wave sleep has restorative effects and is like a period of rest for the brain. Without rest, our brain can't function properly.
* During sleep we can reorganize and store information. Neurons involved in memory and attentive learning rest during sleep, especially during REM.
REM sleep plays a role in memory retention and consolidation.
* REM sleep may remove useless information from memory. This theory suggests its equally important to remove unwanted information and to store
* Sleep may play a role in the brain's development. REM sleep is a major component of sleep for babies in utero and infants and REM is thought to
activate visual, motor and sensory areas in the brain. In the baby's brain, this increases the ability of neurons to make the correct connections and
* Sleep may be an adaptive behavior to keep us away from trouble at night. In a natural environment we're daytime beings; in the darkness of night
we can't perform the same activities we engage during the day. So by sleeping we refrain from being active at night when our vision is poor and this
keeps us away from trouble.
* Sleep is so essential that long periods of sleep deprivation eventually results in stress-related deaths. Missing even 1 single night of sleep may
affect our mental performance in decision making the next day.
* Sleep spindles and K complexes may help us disconnect from the outside world (noises, etc). Elderly have fewer sleep spindles and are easy to wake
* During stage 3 and 4 of sleep, growth hormone is secreted by the pineal gland. This hormone encourages bone and muscle growth in children, while
in adults it is involved in tissue repair. This is another reason slow wave sleep has restorative effects.
* Other hormonal activities, like the secretion of prolactin and gonadotropin occur in these stages, making slow wave sleep a phase of rest and
* The reason we might lose muscle tone during sleep is so we don't act out our dreams and to keep us away from trouble.
* REM sleep may be an evolutionary adaptation to wake up and be fully alert to a potential emergency in the middle of sleep.
* Blood flow to the brain is increased during REM
* Genital activity (in males, penis erection and in females, vaginal secretions, these not necessarily indicate that the sleeper is experiencing a
dream of sexual content).
* REM sleep is believed to occur to allow the brain to further develop and to promote learning, memory and motivation. This may explain why we often
feel unmotivated to learn or concentrate when we're lacking sleep.
* There are 2 principles regarding why we sleep. Sleep serves as an adaptive response to our environment or serves as restoration for the mind. The
fact that all vertebrates sleep seems to imply that sleep occurs more as an adaptive response than to serve as rest for the mind. However, slow-wave
sleep, with its 2 deepest stages of sleep, appears to serve as a way for the body and mind to rest and recuperate.
* Research has shown that lack of sleep causes the inability for one to perform cognitive tasks well. The same tasks are performed with much more
proficiency when sleep has been acquired. REM sleep appears to possibly occur for brain development and thus, learning, memory and motivation. REM
may serve to allow for brain development to occur. Although research has shown that REM sleep isn't needed for the body itself to perform its daily
functions, the "rebound phenomenon" will occur if one fails to receive enough REM sleep. The rebound phenomenon refers to the idea that a nightís
sleep will be composed for more than its usual REM sleep if the previous nightís sleep didnít involve enough.
* In furthering the discovery of REM state as the dreaming state, other research set out to examine if dreaming existed as a means for survival. It
was wondered if people who were deprived of sleep could continue to function normally. Was dreaming necessary for our physiological well being like
sleep appeared to be, or did it serve a psychological purpose?
* Research has shown that after a succession of dreamless nights, dreaming onset seemed to occur more rapidly after falling asleep and lasted for
longer periods of time. It seemed that our bodies tried to make up any dreaming that was lost over a succession of dreamless sleeps; it seemed our
bodies were pressured to dream. The conclusion is that there must be some biological need for our bodies to not only sleep, but also to dream.
On-going research is trying to pin the exact purpose for dreaming.
* In adults, sleep of 8 to 8.4 hours is considered fully restorative. In some cultures, total sleep often is divided into an overnight sleep period
of 6 to 7 hours and a midafternoon nap of 1 to 2 hours.
* Infants have an overall greater total sleep time than any other age group
* In elderly, the time spent in stages III and IV sleep decreases by 15% and the time in stage II increases by 5% compared to young adults,
representing an overall decrease in total sleep duration. Latency to fall asleep and the number and duration of overnight arousal periods increase.
This means the person needs to sleep more to feel restored. If the elderly person doesn't increase his total time in bed, complaints of insomnia and
chronic sleepiness may occur. Sleep fragmentation results from waking up in the middle of sleep and may be elicited by the increasing number of
geriatric medical conditions, including sleep apnea, musculoskeletal disorders, and cardiopulmonary disease.
Some sleep websites:
The National Sleep Foundation:
The American Academy of Sleep Medicine:
The Sleep Research Society:
The World Federation of Sleep Research Societies:
The International Sleep Medicine Association: