TEMPORAL ORGANIZATION OF SLEEP-WAKE STATES IN PRETERM INFANTS

The development of temporal organization of sleep-wake states during t he preterm period was examined. Seventy-one high-risk preterms from tw o cohorts were observed from 7 to II p.m. weekly from the time they we re no longer critical until discharge. Mixed general linear model anal yses found that with increasing postconceptional age, quiet waking, ac tive waking, and sleep-wake transition bouts occurred more frequently, quiet sleep bouts occurred less frequently, and active waking and qui et sleep bouts increased in length. However, these developmental patte rns were not stable over cohorts. On the other hand, the transitional probabilities between states were similar in both cohorts, providing e vidence for biological bases for some aspects of temporal organization . Active sleep was pivotal in state transitions. Younger infants showe d fewer transitions that did not involve active sleep. Thus, temporal organization is an early characteristic of sleep-wake states but is no t a unitary phenomenon. Transitional probabilities remain relatively i nvariant, whereas bouts lengths and frequencies may be altered in diff erent populations or by differing environmental conditions. (C) 1998 J ohn Wiley di Sons, Inc.