Objective: To examine the effects of changes in sleep phase on the daytime functioning of new university graduates. Methods: Questionnaire data of university students (n = 745) and university graduates working full time (n = 360) were analyzed to explore sleep phase changes during this life stage. The newly graduated full-time workers (n = 117) were divided into 2 (bedtime at investigation: earlier/later) × 2 groups (bedtime at one year prior to investigation: earlier/later), and depressive symptoms and health-related quality of life were compared among groups. Results: New university graduates experienced ~1 h of sleep phase advancement and shortened time in bed compared to one year before investigation. In addition, those who experienced such sleep changes showed larger daytime dysfunction. Conclusion: Prevention of extreme sleep phase delay during university days might be helpful for students' adaptation to work environment after graduation.
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