Daily light exposure, sleep-wake cycle and attention in adolescents from different urban contexts

Objective: to compare daily light exposure, activity-rest rhythm, sleepewake cycle (SWC) and attention in Brazilian students living in different levels of urbanization. Methods: 115 adolescents (74 girls), aged 14-18 years (mean 15.5 +/- 0.7 years), from the first years of high school have participated. The SWC was evaluated by actimetry and a Sleep Diary for 10 days. Besides, the Health and Sleep Questionnaire, the Morningness and Eveningness Scale for adolescents, the Pittsburgh Sleep Quality Index, and the Pediatric Daytime Sleepiness Scale were answered. Attention was assessed by a Continuous Performance Task. Results: In the less urbanized region, there were a greater exposure to light during the day accompanied by a higher proportion of morning-types and less occurrence of excessive daytime sleepiness. Otherwise, in the more urbanized region, adolescents showed a trend to sleep less in weekdays and presented more irregularity in sleep duration between weekdays and weekend, with 83 +/- 15% of sleep efficiency, 01:04 +/- 1:30 h of WASO and 7 +/- 6.7 awakenings per night on the weekdays, suggestive of poor sleep quality. Despite of this, they showed better attentional performance: more correct responses (tonic and phasic alertness, and sustained attention) and less omissions (for all components). Regardless of the degree of urbanization, there was partial sleep deprivation, irregular sleep schedules and poor sleep quality in adolescents. Conclusions: The daily light exposure and activity-rest profiles, SWC and attention in adolescents varied according to the degree of urbanization. Besides, the negative impacts of early school starting times leading to sleep deprivation, irregular sleep times and poor sleep quality were observed irrespective of the degree of urbanization, reinforcing that the early school starting time at morning is a strong temporal challenge for teenagers, having negative impacts on cognition and academic performance. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

Adolescents living in different levels of urbanization in Brazil showed variations in daily light exposure, sleep patterns, and attention performance. Regardless of the urbanization level, adolescents faced challenges such as partial sleep deprivation, irregular sleep schedules, and poor sleep quality, with negative impacts on cognition and academic performance.