Programa de Neuropsicología y Neurobiología, Facultad de Psicología, Universidad de la República, Uruguay.
Laboratorio de Neurociencias, Facultad de Ciencias, Universidad de la República, Uruguay.
J Biol Rhythms. 2020 Aug;35(4):391-404. doi: 10.1177/0748730420927601. Epub 2020 Jun 1.
During adolescence, biological, psychosocial, and contextual factors converge in a "perfect storm" and have been put forward to explain the delay in chronotype observed at this age and the prevalence of disrupted sleep. This study provides evidence to support that chronotype and sleep patterns (particularly sleep duration) are socially constrained and to identify novel significant social predictors. Uruguayan public school activities are arranged in up to 4 shifts, creating a natural experiment to examine the effect of school timing on questionnaire-based assessments of sleep and chronotype. In this study, 268 high school students (15-18 years old) who attended school either on morning (0730 to 1130 h) or afternoon shifts (1130 h to 1530 h) responded to an adapted School Sleep Habits Survey. Students attending afternoon shifts had later chronotypes (a 1.5-h later midpoint of sleep on free days adjusted for sleep debt) than those attending the morning shift. Besides shift, evening social activities (including dinner time) were further identified as key predictors of late chronotypes, whereas age and gender were not. Sleep on school days was overall advanced and reduced with respect to weekends, and these effects were stronger in morning-shift students. Weekend sleep duration was similar between shifts, which probably caused the prevalence of reduced sleep durations (average weekly sleep duration, SDweek <8 h) to be higher in morning-shift students (almost 80%) than in afternoon-shift ones (34%). Reduced sleep duration was significantly higher in morning-shift students. In addition, age, chronotype, and dinner time became relevant determinants of sleep deficit only in the morning-shift students. Besides the important social constraint of early school start time, this is the first study to confirm the significance of other types of social pressures on both adolescents' chronotype and sleep deficit, which can be useful as potential new targets for effective policies to protect adolescent sleep.
在青春期，生物、心理社会和环境因素汇聚在一起，形成了一场“完美风暴”，这被认为是导致这个年龄段的时型延迟和睡眠紊乱流行的原因。本研究提供了证据支持时型和睡眠模式（特别是睡眠时间）受到社会限制，并确定了新的重要社会预测因素。乌拉圭的公立学校活动分为多达 4 个时段，这为研究学校时间安排对基于问卷的睡眠和时型评估的影响提供了自然实验。在这项研究中，268 名 15-18 岁的高中生分别参加上午（07:30 至 11:30）或下午（11:30 至 15:30）时段的课程，并对经过调整的学校睡眠习惯调查问卷做出了回应。与参加上午时段课程的学生相比，参加下午时段课程的学生时型更晚（在调整了睡眠债务后，自由日的睡眠中点延迟了 1.5 小时）。除了时段，晚上的社交活动（包括晚餐时间）被进一步确定为导致晚时型的关键因素，而年龄和性别则不是。与周末相比，上学日的整体睡眠时间提前，减少，这种影响在参加上午时段课程的学生中更强。两个时段的周末睡眠时间相似，这可能导致参加上午时段课程的学生（近 80%）比参加下午时段课程的学生（34%）更易出现睡眠时间减少（平均每周睡眠时间，SDweek<8 小时）。睡眠时间减少在参加上午时段课程的学生中更为显著。此外，年龄、时型和晚餐时间仅在参加上午时段课程的学生中成为睡眠不足的重要决定因素。除了上学时间早的重要社会限制外，这是第一项确认其他类型的社会压力对青少年时型和睡眠不足的重要性的研究，这可以作为保护青少年睡眠的有效政策的潜在新目标。
