Evening naps and delayed night‐time sleep schedule typically found in Japanese adolescents is closely related with their daytime malfunctioning

Fukuda and Ishihara (2001) administered a questionnaire concerning sleep-related lifestyle to junior high and high school students and revealed that night-time sleep length was shortest and several physical and mental conditions were worst at high school age. About a half of junior high and high school students take routine afternoon or evening naps to keep themselves awake to study at night at home and to compensate for their chronic sleep insufficiency. At the same time late naps are known to disturb night-time sleep. This study aimed at investigating relationship between the schedule of evening naps and delayed night-time sleep and daytime functioning in the Japanese junior high and high school students.