The Development of Circadian Rhythms in Human Infants

1.8.3 Ontogeny of Sleep in Infants
Sleep patterns change with age. In neonates, there is reversal in the sleep stages as
demonstrated in adult studies. In adults, sleep begins with non REM sleep (equivalent
to quiet sleep in babies) or deep sleep. Sleep episodes, in infants, begin with active
sleep, which is equivalent to REM sleep. In infants there is an alternating pattern of
sleep between REM and non-REM which lasts for 60 minutes compared to the non-
REM / REM cycle in adults which lasts for 90 minutes (Erwin et al., 1984, Coons &
Guilleminault, 1984).
Inutero, below 28 weeks gestation, most brain wave activity is indeterminate and
cannot be classified into active and quiet sleep. At 28 weeks there is some
differentiation into rest activity cycles. REM (active) sleep predominates. This
alternates with brief periods of quiet (non REM equivalent) sleep. At term, there is a
decreases in the percentage of REM sleep which makes up around 50% of total sleep
duration, according to one study group. At this time there is a corresponding increase
in non-REM or quiet sleep. By 5 to 8 months of age postnatally, recordings show that
non-REM occupies 80% and REM 20%. The EEG now approximates that found in
sleep studies performed in older children/teens and adults as reported by Graven and
Browne (Graven & Browne, 2008). This was similar to findings in a study which
used 24 hour motility signals in term infants on pressure sensitive bedding (Thoman
& Whitney 1989). The predominance of REM sleep in the early postnatal period is a
finding common with newborn mammals other than the human infant and is thought
to be related to the role of REM sleep in brain maturation and development (Frank &
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