Daytime sleepiness and associated factors in Japanese school children.

OBJECTIVE: To examine daytime sleepiness and sleepiness interrelationship with sleep-wake patterns, eating habits, physical activity, and TV/video game time. STUDY DESIGN: A cross-sectional survey with 9,261 school children (mean age of 12.8 years) from 93 junior high schools in Toyama prefecture, Japan. RESULTS: The main outcome measures were daytime sleepiness during schooldays and sleepiness interrelationship with sleep-wake patterns, eating habits, physical activity, and visual media use. A total of 2,328 children (25.2%) reported sleepiness almost always and 4,401 (47.6%) sleepiness often. Regarding sex difference, a higher proportion of girls reported sleepiness in comparison to boys (79% vs 66%, P < .001). Higher body mass index values were associated with the presence of sleepiness. In girls with preferences for daily snack (versus those who reported no snack) sleepiness presented significantly (P < .001) higher values. Reduced sleep time was significantly associated with sleepiness. The prevalence of sleepiness did not significantly differ among groups who had 7.5 hours sleep or more. A dose-response relation was found between sleepiness and sleep disturbances, physical activity, and media use time. CONCLUSIONS: Sleep insufficiency represents a main cause for daytime sleepiness in Japanese junior high school children. Proper sleep habits, high physical activity level, and limited TV viewing time should be promoted among school children.