title: The Impact of Sleep Timing, Sleep Duration, and Sleep Quality on Depressive Symptoms and Suicidal Ideation amongst Japanese Freshmen: The EQUSITE Study.
abstract: Aim. The aim of this study was to identify the impact of bedtime, wake time, sleep duration, sleep-onset latency, and sleep quality on depressive symptoms and suicidal ideation amongst Japanese freshmen. Methods. This cross-sectional data was derived from the baseline survey of the Enhancement of Q-University Students Intelligence (EQUSITE) study conducted from May to June, 2010. A total of 2,631 participants were recruited and completed the following self-reported questionnaires: the Pittsburgh Sleep Quality Index (PSQI), the Center for Epidemiologic Studies Depression Scale (CES-D), and the original Health Support Questionnaires developed by the EQUSITE study research team. Results. Of 1,992 participants eligible for analysis, 25.5% (n = 507) reported depressive symptoms (CES-D total score ≥ 16), and 5.8% (n = 115) reported suicidal ideation. The present study showed that late bedtime (later than 01:30), sleep-onset latency (≥30 minutes), and poor sleep quality showed a marginally significant association with depressive symptoms. Poor sleep quality was seen to predict suicidal ideation even after adjusting for depressive symptoms. Conclusion. The current study has important implications for the role of bedtime in the prevention of depressive symptoms. Improving sleep quality may prevent the development of depressive symptoms and reduce the likelihood of suicidal ideation.
authors.affiliation: Department of Behavioral and Health Sciences, Graduate School of Human-Environment Studies, Kyushu University, 6-1 Kasuga-kouen, Kasuga, Fukuoka Prefecture 816-8580, Japan.
authors.forename: Atin
authors.initials: A
authors.lastname: Supartini
authors.affiliation: Department of Environmental Medicine, Graduate School of Medical Science, Kyushu University, Maidashi 3-1-1, Higashi-ku, Fukuoka City, Fukuoka Prefecture 812-8582, Japan; Research Fellow of the Japan Society for the Promotion of Science, 5-3-1 Kojimachi, Chiyoda-ku, Tokyo 102-0083, Japan.
authors.forename: Takanori
authors.initials: T
authors.lastname: Honda
authors.affiliation: Department of Behavioral and Health Sciences, Graduate School of Human-Environment Studies, Kyushu University, 6-1 Kasuga-kouen, Kasuga, Fukuoka Prefecture 816-8580, Japan.
authors.forename: Nadzirah A
authors.initials: NA
authors.lastname: Basri
authors.affiliation: Department of Behavioral and Health Sciences, Graduate School of Human-Environment Studies, Kyushu University, 6-1 Kasuga-kouen, Kasuga, Fukuoka Prefecture 816-8580, Japan.
authors.forename: Yuka
authors.initials: Y
authors.lastname: Haeuchi
authors.affiliation: Department of Behavioral and Health Sciences, Graduate School of Human-Environment Studies, Kyushu University, 6-1 Kasuga-kouen, Kasuga, Fukuoka Prefecture 816-8580, Japan.
authors.forename: Sanmei
authors.initials: S
authors.lastname: Chen
authors.affiliation: Faculty of Arts and Science, Kyushu University, 6-1 Kasuga-kouen, Kasuga, Fukuoka Prefecture 816-8580, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Ichimiya
authors.affiliation: Department of Behavioral and Health Sciences, Graduate School of Human-Environment Studies, Kyushu University, 6-1 Kasuga-kouen, Kasuga, Fukuoka Prefecture 816-8580, Japan; Faculty of Arts and Science, Kyushu University, 6-1 Kasuga-kouen, Kasuga, Fukuoka Prefecture 816-8580, Japan.
authors.forename: Shuzo
authors.initials: S
authors.lastname: Kumagai