The development of sleeping and waking states in high-risk preterm infants
This study examined the development of sleeping and waking states in high-risk preterm infants. Thirty-seven preterm infants were observed from 7 p.m. to 11 p.m. weekly from the time their conditions were no longer critical until term age or hospital discharge. An average of 3.6 observations was conducted on each infant between 29 and 39 weeks conceptional age (CA). During the observations, the occurrence of eight sleep-wake states was recorded every 10 s. The intensity of rapid eye movements in active sleep and the regularity of respiration in quiet sleep were also rated. Similar state patterns were found at all ages, with active sleep the most frequent state, quiet sleep the second most frequent, and drowsiness and sleep-wake transition third and fourth. Waking states made up only small percentages of the observations at every age. Despite these similarities, four states exhibited significant changes over age: the amount of active sleep decreased, and fuss, cry, and quiet sleep increased. The organization of the sleep states also increased, as evidenced by an increase in the percent of active sleep with rapid eye movements and an increase in the regularity of respiration in quiet sleep. The severity of illness experienced by the infants had only minor effects on these patterns. These findings demonstrate that even high-risk infants show behavioral states by 29 weeks CA and that considerable state development occurs over the preterm period. Additional research is needed to determine the effects of time of day, caregiving environments, and specific insults on state development. © 1990.
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