Lesson 1: Clinical Disorders – Part D

PART D

Sleep Patterns

Sleep patterns change during an individual’s life. In fact, age affects sleep more than any other natural factor. Newborns sleep an average of 16 to 18 hours per day. By the time a child is three to five years old, total sleep time averages 10 to 12 hours, and then it further decreases to 7 to 8 hours per night by adulthood. One of the most prominent age-related changes in sleep is a reduction in the time spent in the deepest stages of NREM (Stages 3 and 4) from childhood through adulthood. In fact, this change is prominent during adolescence, when about 40 percent of this activity is lost and replaced by Stage 2 NREM sleep. In addition to these changes, the percentage of time spent in REM sleep also changes during development. Newborns may spend about 50 percent of their total sleep time in REM sleep. In fact, unlike older children and adults, infants fall asleep directly into REM sleep. Infant sleep cycles generally last only 50 to 60 minutes. By two years of age, REM sleep accounts for 20 to 25 percent of total sleep time, which remains relatively constant throughout the remainder of life. Young children have a high arousal threshold, which means they can sleep through loud noises, especially in the early part of the night. For example, one study showed that 10-year-olds were undisturbed by a noise as loud as the sound of a jet airplane taking off nearby.

Although most humans maintain REM sleep throughout life, brain disorders such as Alzheimer’s and Parkinson’s are characterized by decreasing amounts of REM sleep as the diseases progress. Also, elderly individuals exhibit more variation in the duration and quality of sleep than do younger adults. Elderly people may also exhibit increased sleep fragmentation (arousals from sleep that occur as either short or more extended awakenings). Overall, several issues are important to consider. First, individual sleep needs vary. For instance, eight hours of sleep per night appears to be optimal for most adults although some may need more or less. Teenagers, on average, require about nine or more hours of sleep per night to be as alert as possible when awake. If sleep needs are not met, a progressive sleep debt occurs, and eventually the body requires that the debt be paid. We seem unable to adapt to getting less sleep than our bodies require. Not getting enough sleep, while still allowing us to function in a seemingly normal manner, does impair motor and cognitive functions. Caffeine and other stimulants cannot substitute for sleep, but they do help to counteract some of the effects of sleep deprivation.

Video:  Teenage Sleep