新生児特別養護施設に入院中の未熟児の一日リズムの発達

Abstract

The purpose of the present study is to examine longitudinally and cross-sectionally the development of sleep-in-night and wakefulness-in-day rhythm in preterm infants staying in a Neonatal Intensive Care Unit for a long time. Eight infants in the longitudinal study and 36 infants in the cross-sectional study were individually observed throughout the day with a 24-hr. continuous video recording system. Each infant of the former study was observed for 3 or 6 random days with a random interval of 1 to 5 weeks until the infants reached the predetermined criterion of accomplishing the sleep and wakefulness rhythm. In the latter study, the 36 infants were divided into 3 groups according to age (month) and placed under 24-hr. observation. Behavioral states of the infants for 10 minute periods sampled at two hour intervals of the observing day were determined. Most of the preterm infants in the longitudinal study showed clear sleep and wakefulness rhythms at the age of 14 to 16 weeks. In the cross-sectional study, the infants of the 4 month old group were significantly more wakeful in the day than of the 2 and 3 month old groups. There were no significant differences among the three groups with respect to sleep in the night. The findings of the present study suggest that the development of the sleep-wakefulness rhythm may be genetically determined in preterm infants.