Multiple positive outcomes of a later school starting time for adolescents



      We tested the effect of later school start time (LSST) by 1 hour during 1 week on sleep, sleepiness, and mood profile using within-subject design.


      A within-subject 3-weeks-long interventional study. A baseline week with school starting at 7:30 AM (week A), followed by an intervention week with school starting at 8:30 AM (week B), and a recovery week with school start time back to 7:30 AM (week C). Mixed model for repeated measures analysis was applied to test for the LSST effect between weeks.


      A private high school with high level of socioeconomic status.


      Forty-eight adolescents from 3 different high school years.


      Participants were invited to wear actigraphs continuously during the 3 experimental weeks. Somnolence was obtained every school day twice, at arrival and before departure of school. Sleep quality and mood profile were evaluated by standard measures by the end of each school week, resulting in 3 repeated measures for each variable.


      Thirty-eight adolescents completed the study. Adolescents woke up later during week B (7:42 ± 00:30) in comparison to weeks A (6:54 ± 00:12) and C (6:46 ± 00:15) (p < .001), with no significant change on sleep onset between weeks (p = .657), resulting in a longer sleep duration in week B (p < .001). Significant improvements on sleepiness and mood profile were also reported during week B.


      Starting school later was effective in improving multiple aspects from sleep patterns, subjective sleepiness, and mood profile.


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