SHORT PAPER Comparative study on circadian typology of Japanese and Italian students aged 12–18 years.

The average bedtime and sleep duration of Japanese students aged 12–18 years was later and shorter, respectively, by 1 h compared with those of Italian students. Japanese students aged 12–15 years were predominantly more evening-typed than Italian students, while there were no significant differences in the morningness-eveningness (M-E) scores between students aged 16–18 years in the two countries. The bedtime of approximately 70% of Italian students was fixed by parents during their childhood, whereas the bedtime of only 40% of Japanese students was fixed by their parents. Current bedtime fixation made the students (both Japanese and Italian) aged 12–15 years more morning-typed, while it had no effects on the M-E scores of students 16–18 years. [ABSTRACT FROM AUTHOR]