*Correspondence author e-mail: ericofelden@gmail.com Introduction: Several studies have shown that during weekdays adolescents generally sleep on average considerably less than the recommended 9h/day. This sleep deprivation has been attributed in great part to a sleep phase delay, which occurs for biological and socio-cultural reasons. The aim of this study was to depict some environmental factors related to adolescents sleep length. Methods: A total of 1140 students (569 males), aged 10-19 years, attending two schools of rural regions of Paraná State in southern Brazil, completed a questionnaire about their sleep habits. Demographic data were also obtained. Prevalence ratios (PR) were estimated for more than nine hours of sleep on weekdays. Sleep duration in adolescents with and without electric lighting at home was compared by means Kruskal-Wallis test. Results: Average sleep duration was 9.63(±1.64)h during weekdays and 10.l4(±2,42)h during weekends. The prevalence of adolescents with more than nine hours of sleep during weekdays was 58.3%. On multivariate analysis, age, work and bedtime were factors associated with sleep duration. The prevalence of more than nine hours of sleep was lower in older students (16-17years) than in younger students (10-1 1 years)(PR=0.93; CI95%:0.87-0.99) and lower in workers than in non-workers (PR=0.92;CI95%:0.89-0.96). Adolescents with later bedtimes (10pm) showed shorter sleep duration when compared to those with earlier bedtimes (9pm)(PR=0.79;CI95%:0.76-0.84). Adolescents without electric lighting at home showed longer sleep duration on weekdays (p<0.001) and on weekends (p<0.01) when compared to those with electric lighting at home. Conclusion: In contrast with data previously reported, a high prevalence of adolescents with more than nine hours of sleep during weekdays was found. Data on populations living in less industrialized regions reinforce the idea that technological advances are associated with the negative impact of the sleep phase delay in adolescents. Publication History Article published online: 16 June 2026 © 2009. Brazilian Sleep Academy. This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/) Thieme Revinter Publicações Ltda. Rua Rego Freitas, 175, loja 1, República, São Paulo, SP, CEP 01220-010, Brazil
Pereira et al. (Thu,) studied this question.