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Investigators from multiple institutions conducted a meta-analysis to assess the association between school start time (SST) and sleep and other developmental outcomes in youths. For the study, they systematically reviewed published articles and identified studies that measured SST, sleep, or other developmental outcomes and were published in English. The following outcomes were assessed: sleep, socioemotional health, academics, cognition, and behavioral health (eg, substance use). An aggregate developmental outcome also was developed. Specific sleep indicators including duration, quality, bedtime, wake time, sleepiness, chronotype, hygiene, and naps were assessed. The initial analysis focused on the overall association of SST with these outcomes. The analyses were repeated with SSTs and grouped into different time categories (eg, before 7:30 a.m., 7:30 a.m. to 7:59 a.m.). The effects of changing SST on the outcomes were assessed. Finally, effect sizes by school characteristics (high school vs middle school, private vs public) were evaluated. Multiple meta-analysis regression techniques were used to identify statistically significant associations.
The meta-analysis included data on 1,774,509 participants from 28 studies. Overall, later SST was associated with significantly better outcomes, as measured by the aggregate developmental outcome (P = 0.01). Among specific outcomes, later SST was associated with longer sleep duration (P = 0.02) and lower levels of negative socioemotional well-being (P = 0.04); there was no significant relationship between academics and SST (P = 0.70). Compared with SST before 7:30 a.m., SST between 7:30 a.m. and 7:59 a.m. were associated with a better aggregate development outcome (P = 0.02). Changing SST to 8:30 a.m. to 8:59 a.m. from an 8 a.m. to 8:29 a.m. start time was associated with improvement in the aggregate developmental outcome (P = 0.02) and longer sleep duration (P = 0.02). Compared to middle school students, later SST was associated with significantly less sleepiness (P = 0.01) in high school students, and the positive effect on later wake times was significantly greater for those in private vs public schools (P = 0.04).
The authors conclude that later SST was associated with better overall developmental outcomes, longer sleep duration, and less negative mood.
Dr Dubik has disclosed no financial relationship relevant to this commentary. This commentary does not contain a discussion of an unapproved/investigative use of a commercial product/device.
With puberty, the circadian system naturally delays such that bedtime and wake time are later than before.1 This can be aggravated by modern social factors. Adolescent sleep patterns differ on school days and non-school days, with truncated sleep during the week and catch-up sleep on weekends and holidays.2 It is as if the teenager had flown east across 2 to 3 time zones and suffered from jet lag. This disconnect between social time and biological time is called “social jet...
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