[Development of nocturnal sleep behaviors in very low birth infants].

The objective of this study is to identify the developmental changes in nocturnal sleep behaviors among preterm infants in comparison with full-term infants (control group). The subjects were 18 preterm infants and 23 full-term infants with mean gestational weeks of 26.5 +/- 2.3 and 39.1 +/- 1.3, and average weights of 879 +/- 188 g and 2,940 +/- 352 g, respectively. Sleep measures were obtained through Actigraph (Micro-mini RC, Ambulatory Monitoring Inc., Ardsley, NY) over a week-long period. Results showed that the sleep duration was significantly different depending on the corrected age of months in only the preterm group (Preterm group: 504 +/- 55 min in under 12 months group, 543 +/- 68 min in over 13 months group. Full-term group: 548 +/- 68 min in under 12 months group, 544 +/- 79 min in over 13 months group). ACTX (percentage of minutes with higher than 0 activity score) was significantly higher for the preterm infants at both age groups in months. In conclusion, the nocturnal sleep duration of preterm infants reached the same level as those of full-term infants after the age of 13 corrected months. Also preterm infants were found to have a higher percentage of less restful sleep during nighttime. Further research is needed to understand the developmental course of physical activity during night time of preterm infants.