Comparative study on circadian typology and sleep habits of Japanese and Czech infants aged 0-8 years

Average bedtime and sleep duration of Japanese infants aged 0-8 years were later by 1.3 h and shorter by 1 h, respectively, than those of Czech infants. Japanese infants were predominantly more evening-type than Czech infants, while Japanese parents (mostly mothers) were significantly more morning-type than Czech mothers. Correlation value (r-value) between the morningness-eveningness (M-E) scores of infants and mothers was 0.405 in Japanese participants, whereas it was relatively low (0.297) in Czech ones. Czech infants were reported as being depressed more frequently than Japanese ones who were reported as being more frequently angry than the Czech infants.