Objective: Sleep affects adolescents in various ways. However, the effects of multiple factors on sleep hygiene remain unclear. A comprehensive assessment of the effects of life habits on sleep in high-school students was conducted. Methods: A cross-sectional survey of 344 high school students (age range 15–17; 171 boys, 173 girls) in Tokyo, Japan was conducted in 2015. Complete responses were provided by 294 students. Demographic variables, Pittsburgh Sleep Quality Index (PSQI), diurnal type scale, Pediatric Daytime Sleepiness Scale (PDSS), and life habits such as dinnertime, viewing electronic displays, caffeine intake, sunlight in the morning, and the brightness of the room in the night were asked. Results: The mean scores were PSQI: 5.9 (±2.3), PDSS: 19.0 (±5.8), and the diurnal type scale: 16.7 (±3.4). Using an electronic display in bed (OR = 3.01; (95%CI) 1.24–7.30), caffeine intake at night always (OR = 2.22; 1.01–4.90), and waking up before dawn (OR = 3.25; 1.34–7.88) were significantly associated with sleep disturbance. Irregular timing of the evening meal (OR = 2.06; 1.10–3.84) and display viewing within 2 h before bedtime (OR = 2.50; 1.01–6.18) or in bed (OR = 3.60; 1.41–9.21) were significantly associated with excessive daytime sleepiness. Using an electronic display within 2 h before bedtime (OR = 2.64; 1.10–6.38) or in bed (OR = 3.50; 1.40–8.76) and a living room which is bright at night (OR = 1.89; 1.06–3.36) were significantly associated with eveningness. Conclusion: Each type of sleep-related problem had its own associated life habit factors.
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