A Nationwide Cohort Study of Parasomnias Among Adolescents.

To elucidate the incidence rates and predictive factors for parasomnias (disorders of arousal, nightmare, and sleep paralysis) in adolescents. This was a prospective cohort study of high school students. In 2010, we conducted a baseline survey of first-year students enrolled in randomly selected Japanese schools (10 junior high schools and 14 senior high schools); 2 years later, a follow-up survey of the same participants was conducted. A self-administered questionnaire inquiring about parasomnias and lifestyles was provided to the students for both surveys. The incidence of new onset of each parasomnia was determined based on the longitudinal survey data obtained at 2 timepoints (ie, baseline and follow-up), separately for the junior and senior high-school students. Moreover, we performed multivariate analyses to identify the predictive factors for new onset of each parasomnia. 776 junior high school students and 2,697 senior high school students participated in both surveys (total response rate: 61.1%). The incidence rates of disorders of arousal, nightmares, and sleep paralysis during the observation period were 14.0%, 16.2%, and 3.3%, respectively, among junior high school students, and 15.1%, 27.8%, and 6.8%, respectively, among senior high school students. The predictive factors (adjusted odds ratio, value) for new onset of disorders of arousal were female sex (1.38, .009) and sleep duration of less than 5 hours (1.95, .001). The predictive factors for onset of nightmares were female sex (1.82, < .001), enrollment in senior high school (vs junior high school) (2.14, < .001), poor subjective sleep quality (1.60, .010), and spending less than 2 hours studying after school hours (1.64, .027). The predictive factors for new onset of sleep paralysis were enrollment in senior high school (vs junior high school) (2.39, .002) and poor mental health status (1.98, < .001). Our study results suggest that sleep status, lifestyle, and mental health are predictive factors for new onset of parasomnias in adolescents. These should be key areas of focus in school health services.