The effects of sleep extension on sleep and cognitive performance in adolescents with chronic sleep reduction: an experimental study.

OBJECTIVE To investigate the effects of gradual sleep extension in adolescents with chronic sleep reduction. Outcome variables were objectively measured sleep and cognitive performance. METHODS Participants were randomly assigned to either a sleep extension group (gradual sleep extension by advancing bedtimes in the evening) or to a control group (no instruction). Our sample consisted of 55 adolescents (mean age, 15.44 y; 85.5% girls) with symptoms of chronic sleep reduction (loss of energy, shortness of sleep, sleepiness, and irritation). Sleep was monitored with actigraphy over 3 weeks; the first week was the baseline week and the last two weeks were the experimental weeks. Participants in the experimental group were instructed to extend their sleep during the week by gradually advancing their bedtimes by 5 minutes each night. Additionally participants were asked to prevent bedtime shifts on weekend nights. Cognitive performance was assessed before and after the experimental manipulation. RESULTS During the last week of the experiment, adolescents in the sleep extension group had earlier bedtimes, earlier sleep onsets, spent more time in bed, and slept longer than adolescents in the control group. These results indicate that the experimental manipulation was successful and that adolescents in the experimental group fell asleep earlier and slept longer than adolescents in the control group. Furthermore some aspects of cognitive performance, especially visuospatial processing, significantly changed in the sleep extension group. CONCLUSION Gradual sleep extension has beneficial effects on adolescents' sleep and is related to changes in some aspects of cognitive performance.