Multiple positive outcomes of a later school starting time for adolescents.

Background and objectives: Adolescents are chronically sleep-deprived. Early school start time is a major promoting factor of adolescent’s sleep deprivation. We evaluate the effect of delaying the school start time (DSST) by one hour during one week on sleep, sleepiness, cognition, and emotion using withing-subject design.Methods: This interventional study enrolled 48 adolescents. Sleep timing and duration was derived from 18 days of actigraphy recording, before, during and after DSST. Baseline, interventional and post-interventional evaluation of sleep quality, mood, and cognition was performed using standard questionnaires. Repeated measures ANOVA was performed to test variables between the weeks of the study.Results: A total of 38 students (age mean 16±0.81 years old) concluded all study steps. Sleep duration increased during the intervention week (A=7:03±0:41; B=7:35±0:48; C=6:46±0:48; p<.01), due the delaying waking up time (A=6:54±0:12; B=7:42±0:30; C=6:46±0:15; p<.01) and no changes in bedtime (A=23:18±0:42; B=23:29±0:36; C=23:28±0:41; p=0.27). DSST also reduced somnolence measured by two independent questionnaires (KSS p<0.01; ESS p<0.01) and improved several aspects of mood measured by POMS and HADS Depression subscale (p=0.004). Improvements in the N-Back test were found, but no effects on free-recall were obtained.Conclusions: Adolescents slept longer during DSST and did not change sleep onset. Starting school later was effective in improving multiple aspects from sleep patterns, subjective sleepiness, emotion and cognition. We add compelling evidence to the beneficial effects of DSST and this practice must be considered by the educational sector.