Hormones 2016

Sleep
The muscles of the body are virtually paralyzed. The brain is highly active
during REM sleep, and the overall brain metabolism may be increased by
as much as 20%. The electrical activity recorded in the brain during REM
sleep is similar to that which is recorded during wakefulness.
Sleep at Different Stages of Life
Infancy
Infants have an overall greater total sleep time than any other age group.
Their sleep time can be divided into multiple periods. In newborns, the total
sleep duration in a day can be 14 to 16 hours. Over the first several months
of life, sleep time decreases; by age 5 to 6 months, sleep consolidates into an
overnight period with at least one nap during the day.
REM sleep in infants represents a larger percentage of the total sleep
at the expense of stages III and IV. Until age 3 to 4 months, newborns
transition from wakefulness into REM sleep. Thereafter, wakefulness begins
to transition directly into NREM sleep.
Adulthood
In adults, sleep of 8 to 8.4 hours is considered fully restorative. In some
cultures, total sleep is often divided into an overnight sleep period of 6 to 7
hours and a nap of 1 to 2 hours.
Some people may need as little as 5 hours or as much as 10 hours of sleep
every day. The period of time a person sleeps depends also on the fact
whether he or she has been deprived of sleep in previous days. Sleeping
too little creates a "sleep debt." This debt needs to be adjusted by sleeping
for longer periods over the next few days. People who sleep less have an
impairment of judgment and reaction time.
Old age
People tend to sleep more lightly and for shorter periods as they get older.
In elderly persons, the time spent in stages III and IV decreases by 10% to
15%, and the time in stage II increases by 5% compared to young adults,
representing an overall decrease in total sleep duration.
Time taken to fall asleep and the number and duration of overnight arousal
periods increase. Thus, to have a fully restorative sleep, the total time in bed
must increase. If the elderly person does not increase the total time in bed,
complaints of insomnia and chronic sleepiness may occur.
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Version 2016.3576– – Document LATEXed – 1st May 2016
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