Sleep and Its Disorders in Children

Timothy F. Hoban, MD

Disclosures

Semin Neurol. 2004;24(3) 

In This Article

Normal Sleep in Infants and Younger Children

The duration and distribution of normal sleep evolve considerably during the first several years of life. Newborn infants may spend up to 16 to 18 hours per day asleep, usually in the form of 3- to 4-hour sleep periods spanning both daytime and nighttime hours.[1] Beginning in the first month of life, these sleep periods begin to adapt to a day-night cycle and other environmental cues, with gradual lengthening of both nighttime sleep period and daytime wakefulness. By 6 months of age, total sleep duration averages 14.2 hours and the longest period of continuous nighttime sleep lengthens to ~6 hours.[1,2] Between 1 and 2 years of age, total sleep time declines from an average of 13.9 hours to 13.2 hours while daytime sleep consolidates into a single nap, usually in the afternoon. Most children give up daytime napping about age 3 and overall sleep time declines gradually to an average of 11.4 hours by 5 years of age.[2,3]

In addition to these considerable changes in sleep duration and distribution during early childhood, important qualitative changes in sleep stages and architecture also occur. Term newborns exhibit poorly differentiated sleep states on electroencephalography (EEG) and polysomnography (PSG). Infants spend up to 50% of sleep time in rapid eye movement (REM) sleep, also known as "active sleep," and usually enter sleep through an initial REM period.[4] REM sleep periods recur in cycles every 50 to 60 minutes, alternating with periods of non-REM (NREM) sleep, sometimes called "quiet sleep." Sleep-onset REM begins to subside by 3 months of age and overall REM sleep declines to less than 30% of total daily sleep by 3 years.[1] Sleep cycle length matures more gradually and an adult cycle length of 90 to 100 minutes is attained only during adolescence.[4]

Typical PSG and EEG markers of specific sleep stages are not fully developed in term neonates but evolve predictably during infancy. Rapid eye movements may be recorded in even premature infants as young as 28 weeks gestational age, but REM-related muscle atonia remains quite variable even in term infants.[5,6,7] Sleep spindles first become evident ~4 weeks of age with development of mature forms by 8 weeks.[8] K-complexes are first seen by 6 months of age and have mature forms by 2 years.[9]

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