REM and NREM sleep duration differs as a function of nighttime interval in infants at high risk for SIDS

Differences in the duration of REM and NREM sleep during the late night and early morning hours when babies are usually asleep and SIDS is most likely to occur were analyzed in infants at high risk for SIDS and rigorously matched normal controls. A 24-72 hr. electrophysiological study of sleep variables was carried out in 1-6 mo. old infants whose age at the time of recording corresponded to the peak age of SIDS (2-4 mo.). 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 to determine whether disturbances in the duration of REM (active) and NREM (quiet) sleep are present in late night and early morning sleep which may contribute to the high frequency of early morning SIDS deaths. The data show that from 23:00-2:00 hrs., R and C infants do not differ either in the total duration or in the percent of total sleep time (TST) in REM sleep. At 2 a.m., the two groups diverge. An abrupt increase in REM sleep occurs in R and a decrease in C infants. These statistically significant differences persist until 11 a.m. This is coupled with a decline in NREM sleep in R and an increase in C infants at the corresponding time intervals. Transitional (T) sleep does not differ in the two groups. These state related changes in nighttime sleep may indicate a subtle neurological deficit in vulnerable infants