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We surveyed the sleep-wake patterns and lifestyle habits in a sample of Japanese first to third year junior high school children (n=638, age 12 to 15 yrs), of whom 29.3% were evening type, 64.1% intermediate type, and 6.6% morning type in preference. The morningness-eveningness (M-E) score was lower (more evening typed), 16.1 vs. 15.4 in first compared to third year students. There were significant gender differences, with girls showing a greater evening preference. Evening preference was associated with longer sleep latency, shortened sleep duration during schooldays and weekends, bad morning feeling, and episodes of daytime sleepiness. In contrast, morning preference was associated with higher sleep drive and better sleep-wake parameters and lifestyle habits. Our results suggest the morning preference should be promoted among junior high school children to increase the likelihood of more regular sleep-wake patterns and lifestyle habits.

BACKGROUND: The validity of sleep quality and quantity indices as reported by schoolchildren has not been established. The purpose of this study is to evaluate the relationship between subjective sleep habits estimation and objective measurement data in schoolchildren. METHODS: The study consisted of 42 healthy junior high school children aged 13-14. Sleep log information was gathered over 7 consecutive days, using a sleep-monitoring device (Actiwatch ® ) and a questionnaire which covered the following aspects for sleep quality and quantity: bed time, sleep latency, sleep start, sleep end, wake up and assumed sleep length. The means of the sleep indices for 5 weekdays were used for analysis. Pearson’s correlation coefficients and paired t-tests were used to evaluate the correlation and difference between subjective and objective sleep parameters. RESULTS: The correlation coefficient between subjective and objective records was 0.49 (p<0.001) for sleep latency, 0.99 (p<0.001) for sleep start time, 0.99 (p<0.001) for sleep end time, and 0.97 (p<0.001) for assumed sleep length. The difference between subjective and objective records was 7.67 min (95% confidence interval [CI]: 4.64-10.71) for sleep latency, and 0:02 min (95% CI: −0:01-0:05) for sleep start time, 0:02 min (95% CI: 0:01-0:03) for sleep end time, and 8.19 min (95% CI: 4.93-11.45) for assumed sleep length. CONCLUSIONS: Although children tended to overestimate sleeping hours, the correlation between subjective and objective sleep indices except sleep latency was quite high. Thus, children’s sleep questionnaire can be applied to surveys for sleep habits screening.

Aims: To investigate associations between mothers' employment (full, part time and no employment) and nutrition habits (regularity of breakfast, snack, dinner, meal speed and portion size) in a sample of Japanese junior high schoolchildren, 12-13 years of age. Methods: A total of 10 453 children aged 12-13 years from the Toyama birth cohort study (fourth phase) participated, of whom 8906 children (89% response rate) responded to all questions related to the examined variables. Nutrition habits consisted of breakfast, snack, dinner, meal speed and meal portion. Children's obesity/overweight was measured by body mass index (BMI). Results: Fathers' employment had no effect on their children's nutrition patterns. Children of full-time employed mothers were the most likely to snack and to skip dinner. Children of part-time employed mothers ate larger meal portions, and those of nonemployed mothers reported faster meal speeds. BMI was significantly (Po0.001) higher among children of full-time employed mothers (19.3), and lowest among non-employed mothers (19.00). Children of full-time employed mothers are more likely to be overweight, but not obese compared with other children. Conclusion: There was a strong relationship between mother's employment and nutrition patterns in this cohort of Japanese schoolchildren; special programs focused on children's nutrition patterns should take into account the mothers' employment status.

SUMMARY The purpose of this study was to investigate the relationships between sleep onset latency (SOL) and other sleep-wake patterns and media use habits in Japanese schoolchildren. A total of 9718 junior high school children responded (12.8 years) and 9199 questionnaires were used in the present analyses. The questionnaire assessed sleep-wake patterns, TV viewing and videogame habits. Overall, 72.1% of the subjects reported short SOL (£20 min). Long SOL subjects (>20 min) were strongly associated with disturbed sleep manifested especially by increased risk of night awakenings, decreased sleep depth, and bad sleep in general (overall sleep quality). Prolonged SOL was also associated with daytime sleepiness, difficulties in falling asleep, bad morning feeling and sleep insufficiency. We found a U-shaped relationship between sleep period and SOL. Increase in bedtime was accompanied by increased risk of prolonged SOL. The impact of ultra-short and ultra-long SOL (£5 and ‡40 min) was also analysed. Long durations of watching television and playing videogame were significantly associated with prolonged SOL. After adjustment for sex, girls presented significantly higher risk of prolonged SOL. Body mass index adjustment did not reveal any significant results. SOL presents a significant component of sleep-wake habits; poor sleep hygiene and insufficient sleep time significantly increase SOL. Parents, healthcare practitioners and children themselves should be aware of the potentially negative influence of prolonged SOL. Additionally, the optimal coherent sleep-wake schedule must be promoted in parallel with the limitation on the viewing TV and game practices.

BACKGROUND: There is little information about validation of young children’s self-reported physical activity. This study assessed the validity of a self-reported questionnaire designed to measure children’s physical activity. METHODS: Subjects were 34 boys from 4th to 6th grade of a public elementary school. Contents of the self-reported physical activity questionnaire included participation in sports club, physical activity intensity, preference for physical activity, and frequency of physical activity. Subjects were equipped with a Lifecorder and an Actiwatch for 7 consecutive days to monitor physical activity. Physical activity index was calculated from the Lifecorder data of total energy expenditure per day (TEE) divided by basal metabolic rate. Unpaired t-test, analysis of variance, and multiple linear regression analysis were performed to clarify the relationship between the objective and subjective data. RESULTS: Subjects who reported participation in a sports club had a higher physical activity index and energy expenditure originating from physical activity than those who did not. Those characterized by a “vigorous” physical activity intensity had a higher physical activity index (1.63±0.08), when compared with peers in “moderate” (1.59±0.06) or “light” categories (1.54±0.07) (p for linear trend p<0.05). A high frequency of physical activity was significantly associated with an increasing trend in energy expenditure originating from physical activity, steps, and activity counts. Preference for physical activity was significantly related to data from the Lifecorder and the Actiwatch. CONCLUSIONS: Schoolchildren’s self-reported physical activity is in accordance with the objective data, and could be used as a valid measure to evaluate physical activity level in school settings.