[Analysis of late bedtime and influencing factors for it with respect to infants' development age and sleep behavior of parents and children].

PURPOSE: To understand influencing factors for late bedtime of infants having nocturnal life, with respect to each development age and sleep behavior of parents and children. We researched on sleep-awake behaviors and ten-day sleep logs of 277 subjects, who registered for a three-year cohort survey. The cohort is recruited at the time of routine examinations for 4 month, 1.5 years, and 3 years, held at three Health and Welfare centers in Fukuoka city in September and October, 2007. We conducted two-way analysis of variance and post-hoc test of Turkey's multiple comparative tests. The independent variables are three age groups (infants, 1.5 years, and 3 years) and three bedtime categories (late: after 22 o'clock, normal: between 21 and 22 o'clock, and early: before 21 o'clock), and the dependent variables are background date, sleep parameter of parents and children, and factors of sleep behavior and so on. The qualitative data including physical conditions, growth status, frequencies of each life activity are analyzed by tabulation, and fulfillment in child raring is analyzed by stepwise multiple linear regression analysis with 15 objective variables, to bring out factors to induce nocturnal life.

RESULTS: Children's bedtime had significant effect for bedtime variables. The bedtime difference was about 40 minutes between the early bedtime group and the late bedtime group. The early bedtime group had the earliest wake-up time among the all age groups, followed by the normal, and then the late bedtime group. Efforts to keep regular sleep and wake-up times were made greatly in the early bedtime group, and the normal and then the late bedtime group followed after. The mothers in the late bedtime group considened an ideal bedtime was around 21h although they were not able to realize it. The lengths of TV viewing and daytime nap had also significant effects for children's bedtimes. As a result of multiple comparisons, there were significant differences between the early and the late bedtime groups and between the normal and the late bedtime groups. For the bedtime of children, only mothers' total sleep hours on weekdays had a significant negative correlation, while all the other parameters were significantly and positively correlated.

DISCUSSION: The study showed influencing factors for bedtime of children were mothers' routine duties in daily life, especially wake-up time, total sleep hours, daytime napping hours of children, and the length of TV viewing. This suggests that further effort on education for sleep environment management is needed.