A one-hour delayed school start improves sleep, sleepiness and inhibitory control in early adolescents in a randomized controlled trial
Abstract
Early school start times (SST) force adolescents to wake earlier than biologically preferred, creating chronic sleep debt. While evidence supports delaying SSTs, few controlled studies have used objective measures to assess their impact. We conducted a controlled intervention in a French boarding school to evaluate the effects of a one-hour delay in SST on sleep (N = 50) and cognitive functioning (N = 73) in early adolescents (age 12.8 years [11.7-14.2], 66% girls). After a baseline period with 8 a.m. starts (T0), four classes were randomized: half remained at the early schedule (Control-SST), half switched to 9 a.m. (Delayed-SST). Sleep measured by actigraphy, cognitive performance and mental health were assessed at baseline (T0) and 6 months later (T1). Between T0 and T1, total sleep time decreased in the Control-SST group, whereas the Delayed-SST group showed a modest, non-significant increase. This resulted at T1 in a 26-min between-group difference (Cohen's d = 0.93, p = 0.007). Sleep onset time did not differ between groups. Sleepiness decreased in Delayed-SST but increased in Control-SST (d = -0.52, p = 0.042). Inhibitory control improved in Delayed-SST compared to Control-SST (d = -0.79, p = 0.001), with trends toward better sustained attention (d = -0.40, p = 0.051). Delaying SST by one hour appears to mitigate the progressive reduction in sleep duration commonly observed during adolescence, and benefits both cognitive functioning and sleepiness outcomes in early…
How strong is the evidence?
Evidence Hub reads this as a randomized trial, done in people. Its evidence level is 2 of 5 (High · randomized trial). Randomized trials of a reasonable size are the strongest single-study design. Reported size: 73 participants or records.
Read the paper
Related studies
- Tryptophan Metabolism and Gut-Brain Homeostasis
- Rationale for a Multi-Factorial Approach for the Reversal of Cognitive Decline in Alzheimer’s Disease and MCI: A Review
- Prioritized Research for the Prevention, Treatment, and Reversal of Chronic Disease: Recommendations From the Lifestyle Medicine Research Summit
- Relationship between sleep disorders and gut dysbiosis: what affects what?
- The role of CLOCK gene in psychiatric disorders: Evidence from human and animal research
- Genetic, Transcriptome, Proteomic, and Epidemiological Evidence for Blood-Brain Barrier Disruption and Polymicrobial Brain Invasion as Determinant Factors in Alzheimer’s Disease
Go deeper in Evidence Hub
Evidence Hub adds a study data sheet (design, sample size, evidence level, key numbers), an AI summary and a chat grounded in the paper's text.