Humans possess an internal 24-hour clock, also called the circadian pacemaker, that partly determines the time when people fall asleep and when they wake, as well as their alertness level while they are awake. One thing that does change, however, is the timing of their sleep. Sleep issues become more common as we age, often beginning in adolescents.Īs children pass into adolescence, both the stages of sleep and the sleep cycle remain largely unchanged. Sleep stages and other patterns are covered in much greater detail in Natural Patterns of Sleep. In other words, sleep is lighter and more fragmented with brief arousals or longer awakenings throughout the night.

Elderly adults typically have relatively short periods of slow-wave sleep and fewer of them. In early adulthood the amount of slow-wave sleep begins to decline. Infants’ and children’s cycles contain a relatively large amount of slow-wave (N3) sleep-the non-dreaming, restorative kind that is also known as deep sleep. Sleep cycles, composed of REM and NREM sleep, last for about 50 minutes in children and 90 minutes in adults. Only during the second six months of life does the system develop sufficiently to inhibit dramatic body movements during REM sleep. Some of these are strong enough to stir the child from sleep. Without full inhibition, brain activity associated with REM sleep can result in dramatic twitches and movements of an infant’s limbs. Interestingly, the neurological barrier that inhibits muscles in the legs and arms from contracting during REM sleep and prevents people from 'acting out' their dreams is also not fully developed in newborns. Not surprisingly, newborns and infants typically spend about twice as much time as adults in REM sleep. REM sleep, which is often associated with dreaming, is thought to assist in brain development, especially early in life. N1 sleep is very light sleep N2 is slightly deeper sleep and N3, also called slow-wave sleep, is the deepest NREM sleep stage. These stages are characterized by increasingly larger and slower brain waves. NREM sleep is broken down into three distinct stages: N1, N2, and N3. These patterns have been classified into two main types of sleep: rapid-eye-movement (REM) sleep and non-rapid-eye-movement (NREM) sleep. During sleep, the brain’s activity changes in characteristic ways over the course of the night. Although it may appear so from the outside, sleep is not a completely inactive state.

Night changes video