Gender and temporal differences in sleep-wake patterns in Japanese schoolchildren.

Study Objective: To determine gender and weekly differences in sleep patterns in Japanese children in junior high school.

Design: A school-based study.

Setting: N/A.

Participants: Ninety-one children, aged 13 to 14 years, from junior high schools in Japan.

Interventions: N/A.

Measurements: Sleep patterns were measured using actigraphy (Actiwatch) for 7 consecutive days, in parallel with daily logs and a questionnaire.

Results: Girls showed better indicators of sleep and higher degrees of motionless sleep during the week. Actual sleep values and sleep efficiency were higher and the fragmentation index was lower in girls compared to in boys. On weekends, bedtime was delayed, especially for boys--11:17 PM versus 10:49 PM for girls. A higher level of activity during sleep was more evident among boys, especially during weekends. Boys also showed a higher number of nighttime awakenings. Subjective complaints such as drowsiness and desire for a longer sleep time were significantly higher for the boys.

Conclusion: Our findings support the hypothesis that, during the junior high school period, the majority of sleep-quality indicators in Japanese schoolchildren were better for girls than for boys. Boys' sleep was less efficient and more fragmented during the entire week in comparison to that of the girls. These objective findings are supported by subjective assessments. Additional studies should clarify whether these disparities are culturally determined or represent a universal gender-specific characteristic.