Chronic sleep restriction triggers inadequate napping habits in adolescents: a population-based study.

BACKGROUND: The prevalence of chronic sleep restriction during adolescence is a major public health issue. Napping has been adopted to alleviate sleep pressure complaints. However, it also has the potential to amplify sleep restriction due to a vicious cycle triggered by delayed sleep times. The aim of this study was to investigate sleep and napping habits in a sample of Brazilian adolescents. METHODS: This study enrolled 1554 high school students and included the evaluation of sleep times, daytime sleepiness, sleep quality, and circadian preference. The students were asked about their napping routine, ie its frequency and duration per week. RESULTS: The adolescent sleep recommendation was achieved by only 27.6% of the sample. Napping habit was reported by 58.1%, with 36.2% of nappers informing naps in 1-2 times per week. Prolonged naps were reported by 44.9% of nappers. Nappers had later median bedtime (23:30) and reduced time in bed (TIB) (median = 07:00 h) compared to non-nappers. The frequency of nappers who did not achieve satisfactory TIB was higher than non-nappers. In addition, nappers reported increased daytime sleepiness and poor sleep quality. Later bedtimes and reduced TIB were associated with longer nap duration. Increased sleepiness and poor sleep quality were linked to a higher nap frequency. CONCLUSIONS: This exploratory survey demonstrated a severe sleep restriction faced by Brazilian adolescents. Napping can be an efficient strategy to counteract sleep restriction, but it needs to be adopted with caution due to the detrimental effects of frequent and prolonged naps on nocturnal sleep.

Effect of morning exercise in sunlight on the sleep-wake cycle in adolescents

A delay in bedtime occurs in adolescence compared with childhood. However, the early waking that morning school hours impose leads to partial sleep deprivation. Although exposure to light is the most important regulator of circadian rhythm in mammals, physical exercise influences circadian synchronization. To assess the effect of morning physical exercise in sunlight on the sleep-wake cycle (SWC) in adolescents, 160 first- and second-year high-school students were exposed to classes in their usual classroom (Group C) or in a swimming pool exposed to sunlight (Group E) while physically exercising (EE; i.e., swimming) or resting (EL). At baseline, we applied Health and Sleep and Horne & Ostberg chronotype assessment questionnaires. One week later and during the intervention, we applied the Sleep Diary and Karolinska Sleepiness Scale. During the intervention we observed no changes in bedtime, time in bed and in indices of irregularity of bedtime and wake-up time. The changes observed in wake-up time (i.e., a delay in the EE group on Saturday), sleep quality (i.e., an improvement), and sleepiness (i.e., an increase) were also observed in the control group, discarding an intervention effect. We suggest that morning physical exercise in sunlight had no effect on SWC parameters, sleep quality, or daytime sleepiness, possibly because of the large irregularity in the SWC between weekdays and weekends in adolescent students as well as the low frequency and duration of exercise during the intervention. Therefore, studies that evaluate a higher frequency or duration of exercise are needed to assess its effect on the SWC in adolescents.

Effect of morning exercise in sunlight on the sleep-wake cycle in adolescents

A delay in bedtime occurs in adolescence compared with childhood. However, the early waking that morning school hours impose leads to partial sleep deprivation. Although exposure to light is the most important regulator of circadian rhythm in mammals, physical exercise influences circadian synchronization. To assess the effect of morning physical exercise in sunlight on the sleep-wake cycle (SWC) in adolescents, 160 first- and second-year high-school students were exposed to classes in their usual classroom (Group C) or in a swimming pool exposed to sunlight (Group E) while physically exercising (EE; i.e., swimming) or resting (EL). At baseline, we applied Health and Sleep and Horne & Ostberg chronotype assessment questionnaires. One week later and during the intervention, we applied the Sleep Diary and Karolinska Sleepiness Scale. During the intervention we observed no changes in bedtime, time in bed and in indices of irregularity of bedtime and wake-up time. The changes observed in wake-up time (i.e., a delay in the EE group on Saturday), sleep quality (i.e., an improvement), and sleepiness (i.e., an increase) were also observed in the control group, discarding an intervention effect. We suggest that morning physical exercise in sunlight had no effect on SWC parameters, sleep quality, or daytime sleepiness, possibly because of the large irregularity in the SWC between weekdays and weekends in adolescent students as well as the low frequency and duration of exercise during the intervention. Therefore, studies that evaluate a higher frequency or duration of exercise are needed to assess its effect on the SWC in adolescents.(AU)

A construção dos tempos escolares / The construction of school times

O presente estudo analisa a concepção de tempo, considerando sua construção sócio-histórica e cultural. Apresenta algumas heranças dos tempos escolares, mostrando que estes são construções humanas e, por isso mesmo, passíveis de transformações. Os tempos escolares fazem referência ao início e à duração da escolarização (tempos de escola); à organização da escolarização (tempos de escolarização); às construções consolidadas no interior das instituições escolares (tempos na escola). Ao apresentar a abrangência da noção de tempos escolares, o presente estudo incita a busca de inovações políticas e escolares que produzam alternativas aos tempos escolares vigentes e indica a necessidade de construir tempos escolares mais humanos, mais atentos às necessidades dos sujeitos da educação.

This study examines the concept of time, given its socio-historical and cultural construction. It presents some legacies of school time, showing that these are human constructions and therefore are subject to change. The school time refers to the starting and the duration of schooling (school term), the organization of schooling (schooling time), and the consolidated constructions within the educational institutions (school time). In presenting the scope of the concept of school time, this study encourages the pursuit of innovation and educational policies that produce alternatives to the current school time and indicate the build a more humanistic and careful school approach towards the needs of the educational subjects.