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A questionnaire concerning sleep-related lifestyle, and physical and mental health was administered to the students of junior high schools (12-15 years), high schools (15-18 years), and universities. While bedtime linearly delayed with age throughout the adolescence (from junior high school to university age), rise time remained constant until high school ages. As a result, total nocturnal sleep time considerably decreased during this period. Rise time then delayed with age in the university sample. Daytime sleepiness increased with age peaking at high school age, then decreased gradually during university age. Several physical and mental health conditions got worse during high school and university ages. Compared with the adolescent samples, daytime sleepiness and mental health complaints were very low in the adult samples.
Fukuda et al. (Fri,) studied this question.