PURPOSE: To find the relationship between parents' sleeping and living behaviors and their children's sleeping habits, and to investigate factors specifically related to children staying up late in recent Japan.
METHODS: During regular health check-ups of children at three local health centers in the city A, we recruited the parents of one-and-half-year-old and three-year-old children to participate in the Child Sleep Cohort Project (ChiSCoP). Parents of 184 children who consented to participation were mailed three questionnaires by placement method. These are "sleeping diary for 10 days," "sleeping and lifetime rhythm survey," and "emotional behavior assessment scale (CBCL : Child Behavior Checklist 2rd/3rd edition)," of which valid data on 178 children were collected over two years and analyzed.
ANALYSIS: Participants' demographic data, perceived and actual sleeping and living habits, and bedtime patterns were compared among the groups classified by bedtime of children. Bedtimes were classified as early (before 21 : 00), normal (21 : 00 to 21 : 59), and late (after 22 : 00). Using one-way analysis of variance with two (early vs. late) and three bedtime categories, significant differences were found among the three bedtime categories about childcare environmental factors (meal, daytime activity, TV, nap, and bath). So we performed logistic regression analysis with "late bedtime" as the dependent variable and scores of environmental factors (upper or lower than median values) as independent variables in a stepwise manner to eliminate collinear variables and to obtain adjusted odds ratios.
RESULTS: 1) Among the 178 children, 96 and 82 were recruited during the physical check-up for one-and-half-year-old and three-years-old, respectively. There were 49, 72, and 57 children in the early, normal, and late bedtime groups, respectively, and no significant difference in attribute factors was found. 2) In children of the early bedtime group, proportions of those with "efforts to establish good life rhythm" (P < 0.0001), "efforts to cultivate sleeping habits" (P < 0.0001), and "keeping a regular bedtime" (P < 0.05) were significantly higher, as well as for children who had more than 105 minutes of "daytime nap" compared to children who had less (P < 0.05). 3) Children's bedtimes were significantly correlated with "mother's wake-up time on weekdays" (r = 0.33) and "mother's bedtime on weekdays" (r = 0.33). Children's wake-up times were also correlated with "mother's wake-up time on weekdays and weekends" (r = 0.49) and "mother's bedtime on weekdays" (r = 0.34), which indicates that children's wake-up times had relationship with mother's sleeping and life habits. 4) Later "wake-up time on weekends" (odds ratio = 4.9) and "regular bedtime hour" (odds ratio = 3.53) were found to be the determinant of late bedtimes of children.
CONCLUSIONS: To encourage earlier bedtimes in children, it is important to take he mother's sleeping and living habits into account and to maintain a regular wake-up and bedtime schedule across weekdays and weekends.
