Predictors of insomnia onset in adolescents in Japan

ObjectiveThe objective of this study was to clarify the incidence rate and predictive factors of insomnia in Japanese junior and senior high school students.MethodsWe conducted a baseline survey on first year junior and senior high school students (seventh and 10th graders) throughout the nation. A follow-up survey was then conducted two years later. For both surveys, we used self-administered questionnaires inquiring about sleep, mental health status, lifestyle, participation in club activities, and study hours.ResultsA total of 3473 students (776 junior high and 2697 senior high) were suitable for analysis. During the two years leading to the follow-up study, the incidence rate of newly developed insomnia was 7.8% among junior high and 9.2% among senior high school students. Multiple logistic regression analyses revealed that factors associated with new insomnia onset were ‘sleep paralysis experience’ and ‘poor mental health status’ in junior high school students, and ‘being woken by a nightmare’, ‘poor mental health status’, ‘≥2 h of extracurricular learning per day’ and ‘mobile phone use for ≥2 h per day’ in senior high school students.ConclusionsIn junior and senior high school students, parasomnias such as nightmares and sleep paralysis, and mental health status can be predictors of insomnia onset. For senior high school students, longer use of mobile phones can be a predictor of insomnia onset. The present findings suggest that sleep health must be promoted among junior and senior high school students in the future.