Correlates of naptime behaviors in preschool aged children.

Purpose: Major changes in the timing, duration, and function of sleep occur during childhood. These changes include the transition from habitual napping to infrequent napping. This transition is likely to reflect, at least in part, neurocognitive development. This study sought to identify factors that discriminate between four groups of children with different teacher-reported responses to naptime in childcare: those who nap (nappers), sometimes nap (transitioners), do not nap (resters), and neither nap, nor lie still (problem nappers). Methods: Standardized observations of sleep and sleep behaviors, daytime behaviors across a number of domains, and direct neurocognitive assessment of 158 preschool aged children (aged 49-72 months; 54% male) attending childcare centers in Queensland (QLD), Australia, were adopted as part of a large longitudinal study of early childhood, the Effective Early Education Experiences (E4Kids) study. Discriminant function analysis was used to examine how age, parent education, nighttime sleep duration, cognitive functioning, behavior problems, and temperament differentiated the four groups. Results: Three discriminant functions were identified and defined as maturation (strong loadings of nighttime sleep duration, cognitive function, and age), socioeconomic status (parental education), and behavioral problems (externalizing behavior, temperament, and internalizing behavior). These functions accounted for 62.9%, 32.6%, and 4.5% of the between-groups variance, respectively. Children defined as nappers (n=44) had significantly shorter duration of nighttime sleep, were younger, and had lower cognitive functioning scores than did other groups. Problem nappers, (n=25) were more likely to have parents with lower levels of education than did transitioners (n=41). Standard behavior and temperament measures did not significantly differentiate the groups. Conclusion: The findings support an interaction between cognitive development, sleep behaviors, and the individual needs and circumstances of children. Further research in this area could make a strong contribution to theory and practice in early childhood education, and a strong contribution to understanding of children's development.

Mandatory Naptimes in Childcare do not Reduce Children's Cortisol Levels.

The majority of preschool children (aged 3-5 years) no longer habitually nap, yet in childcare settings daily mandated naptimes in which children lie down without alternative activity remains a common practice. Mandated naptimes are associated with observed reductions in emotional climate and increased incidence of distress. While intended to be restful, mandatory naptimes may induce stress in those children unable to sleep. To examine this possibility, we applied a 2 (mandated/flexible practice) × 2 (nap/no-nap) design to test group difference in stress responses of children (N = 43, mean age 56.3 months). Salivary cortisol level was measured at 4 time-points (waking, pre-naptime, post-naptime, and bedtime) across two days at childcare. Overall our results show a significant decline in cortisol level from wake to pre-naptime and from post-naptime to bedtime. No significant change in cortisol level was observed from pre- to post- naptime. Significant group differences in cortisol patterns were observed. Notably, children under mandatory naptime conditions who did not nap showed no significant reduction in cortisol level from post-naptime to bedtime. While cortisol measurement suggests naptime is neither stressful nor restful for children in any group, implications for bedtime arousal are raised for those unable to sleep under conditions of mandated naptimes.

Investigating the association between sleep parameters and the weight status of children: night sleep duration matters.

OBJECTIVES: To examine the associations between sleep parameters and weight status in a large sample of preschool children. DESIGN: Cross-sectional survey data from the Effective Early Educational Experiences for children (E4Kids) study were analyzed. PARTICIPANTS: 1111 children aged 3 to 6 years from Queensland and Victoria, Australia. MEASUREMENTS: General linear modeling, with adjustment for significant control variables, assessed the impact of night sleep duration, total sleep duration, napping frequency, sleep timing (onset, offset and midpoint), and severity of sleep problems on standardized body mass index (BMI z score). General linear modeling was conducted for the total sample and then separately by sex. RESULTS: For the total sample, there was a significant association between short sleep duration (≤10 hours) and increased BMI z score. No other sleep parameters were associated with BMI z score in this sample. Analyses by sex revealed that, among girls, there were no associations between any sleep parameter and BMI z score. However, among boys, short night sleep duration and napping frequency were both significantly associated with weight status even after adjustment for controls. CONCLUSION: Night sleep duration is a consistent independent predictor of body mass in young children. These results identify a complex relationship between sleep and body mass that implicates sex. Potential mechanisms that might explain sex differences warrant further investigation.

Mandatory Nap Times and Group Napping Patterns in Child Care: An Observational Study.

Policy provision for naps is typical in child care settings, but there is variability in the practices employed. One practice that might modify children's early sleep patterns is the allocation of a mandatory nap time in which all children are required to lie on their beds without alternate activity permitted. There is currently limited evidence of the effects of such practices on children's napping patterns. This study examined the association between duration of mandatory nap times and group-level napping patterns in child care settings. Observations were undertaken in a community sample of 113 preschool rooms with a scheduled nap time (N = 2,114 children). Results showed that 83.5% of child care settings implemented a mandatory nap time (range = 15-145 min) while 14.2% provided alternate activities for children throughout the nap time period. Overall, 31% of children napped during nap times. Compared to rooms with ≤ 30 min of mandatory nap time, rooms with 31-60 min and > 60 min of mandatory nap time had a two-and-a-half and fourfold increase, respectively, in the proportion of children napping. Nap onset latency did not significantly differ across groups. Among preschool children, exposure to longer mandatory nap times in child care may increase incidence of napping.

Environmental Light Exposure Is Associated with Increased Body Mass in Children.

The timing, intensity, and duration of exposure to both artificial and natural light have acute metabolic and physiological effects in mammals. Recent research in human adults suggests exposure to moderate intensity light later in the day is concurrently associated with increased body mass; however, no studies have investigated the effect of light exposure on body mass in young children. We examined objectively measured light exposure and body mass of 48 preschool-aged children at baseline, and measured their body mass again 12 months later. At baseline, moderate intensity light exposure earlier in the day was associated with increased body mass index (BMI). Increased duration of light exposure at baseline predicted increased BMI 12-months later, even after controlling for baseline sleep duration, sleep timing, BMI, and activity. The findings identify that light exposure may be a contributor to the obesogenic environment during early childhood.

Mandatory Naptimes in Child Care and Children's Nighttime Sleep.

OBJECTIVES: To examine the relationship between mandatory naptimes in child care and children's nighttime sleep duration, both concurrently and 12 months later once in school. METHODS: A sample of 168 children (50-72 months; 55% males) attending licensed child care centers were observed across their morning and throughout their scheduled naptime. Mandatory naptime was determined as the period in which children were not permitted any alternative activity except lying on their bed. Teachers reported each child's napping in child care. Nighttime and total sleep duration was reported by parents at 2 time points, in child care and in the second semester of their first school year. General linear models were used to examine group differences in sleep duration between children experiencing 0 to 60 minutes and >60 minutes of mandatory naptime, adjusting for key confounders. Path analysis was conducted to test a mediation model in which mandatory naptime is associated with nighttime sleep duration through increased napping in child care. RESULTS: Children who experienced >60 minutes of mandatory naptime in child care had significantly less nighttime sleep than those with 0 to 60 minutes of mandatory naptime. This difference persisted at 12-month follow-up, once children were in school. Napping in child care mediated the relationship between mandatory naptime and duration of nighttime sleep. CONCLUSIONS: Exposure to mandatory naptimes of >60 minutes in child care is associated with decreased duration of nighttime sleep that endures beyond child care attendance. Given the large number of children who attend child care, sleep practices within these settings present an important focus for child health.