Throughout our lives our sleep patterns change. For example, newborn babies do not have a 24-hour pattern, but cycle between sleep and wakefulness throughout the day and night. They also do not have discrete sleep stages; they spend about half of sleep time in an “active” stage (similar to REM sleep in adults) and half in a more “quiet” stage (similar to non-REM sleep). Over the first few months of life, sleep begins to consolidate and to resemble adult patterns. By about six months of age, all sleep stages should be recognizable. Infants of this age will usually have a longer nighttime sleep and one or two daytime naps. It is important to note that the amount of sleep a person needs gradually falls during infancy and childhood, reaching adult requirements some time in late adolescence.

As we age, our sleep also changes somewhat (FIGURE 3). After age 50, the total amount of sleep a person requires remains similar to younger adults; however it tends to become more fragmented, with more awakenings during the night. As is common with fragmented sleep, many people have difficulty rising upon waking the next morning and tend to feel tired during the day. The proportion of slow wave sleep decreases relative to total sleep time, but the proportion of sleep that is REM sleep remains largely unchanged.

Figure 3: Effects of Aging on Sleep
Kales and Kales. N. Engl. J. Med.1974;209:487-499

Topic Editor: Carl Bazil, M.D.
Last Reviewed:10/01/05