Abstract
SIDS (Sudden Infant Death Syndrome) is the major cause of death in young, apparently
healthy, infants, yet its etiology and pathogenesis remain unknown. SIDS peaks at
2-4 months, is more prevalent in the winter months and typically occurs in the early
morning hours when most babies are asleep, suggesting that sleep may be part of the
patho-physiological mechanism of SIDS. The sleep patterns of infants at high risk
for SIDS were analyzed to test the hypothesis that there are abnormalities specific
to nighttime sleep which may be indicative of a central nervous system (CNS) deficit
that contributes to a high frequency of SIDS during the night. Electrophysiological
sleep variables were recorded at monthly intervals in 1-6 months-old infants during
the peak age of SIDS. The risk group (R) was resuscitated from a potentially life-threatening
Sudden A-Ventilatory Event (S.A.V.E.) and compared to a group of control infants (C)
with no family history of SIDS. The data representing four equal time intervals from
11 p.m.-11 a.m. show an abrupt, statistically significant increase in REM sleep from
2-5 a.m. in R infants. In C infants, time spent in REM sleep after 2 a.m. becomes
progressively shorter while NREM sleep is proportionately longer. From 11 p.m.-2 a.m.,
however, R and C infants do not differ either in the duration or in the percent of
total sleep time (TST) of REM sleep. We hypothesize that these REM sleep abnormalities
in vulnerable infants are indicative of a pervasive CNS immaturity. The higher prevalence
of SIDS in the cold winter months and in the early morning hours, when darkness is
prolonged, is discussed in relation to the possible involvement of the circadian rhythm
of melatonin.
Key words
SIDS - Abnormal nighttime REM - Infant sleep - Circadian rhythm - Brain immaturity
- Melatonin
