The Relationship between a Night Usage of Mobile Phone and Sleep Habit and the Circadian Typology of Japanese Students Aged 18 - 30 yrs

This study tries to investigate the current relationship between the habit to use mobile phone and the diurnal type scale and sleep habit in Japanese students. An integrated questionnaire was administered to 555 students aged 18 - 30 years old attending university and medical training schools for physical therapists and medical nurses (average age: 19.8 ± 1.6 years) in 2015. Integrated questionnaire included questions on sleep habits, the circadian typology, mental health (out of emotion-control, anger, irritation, depression), meal habits, the diurnal type scale (Torsvall & ?kerstedt, 1980). Most of all students have their own mobile phones and 96% of their phones are “smart phones”. Two hundreds and twenty four students of 531 ones used their phones within 30 min per one usage, whereas 180 students used it 5 - 6 hours per one. There have been significantly no differences in the diurnal type scale scores due to the durations of usage per one usage. Students who put their own mobile phones near to their body during night sleep occupied 461 of 543 students, and they were much more evening-typed than those who put their mobile phones at places far from bed in the same room (p < 0.001). In the cases when night sleep would almost start, phone calls could come from some person, 102 students of 537 ones soon responded to it, whereas 200 ones checked the call but did not respond and felt in sleep. These 302 students were much more evening-typed than 230 students who did not mention this call without checking it and felt in sleep (p < 0.001). The usual life by the students aged 18 - 30 years seems to depend on the usage of smart phones very strictly and may strongly relate to sleep habits and also night usage of smart phones are possible to enhance the evening-typed life.