Sleep duration on a population of children referred to sleep study - cross-sectional data from 2003 to 2009

y Introduction: Sleep is essential for human beings, especially children. Insufficient sleep is linked to somatic and psychological problems. This study aims to describe nocturnal sleep patterns in children aged 7 to 13 years and investigate if sex or weekdays influence sleep habits. It also analyses factors associated with sleep length and the difference between sleep habits on weekends and weekdays. Methods: A retrospective cross-sectional study with questionnaires from children with sleep complaints referred to our service (December 2003 to June 2009) in Sao Paulo City, Brazil. Median of sleep hours, time going to bed, waking up, and the difference in amount of sleep during weekends and weekdays were calculated. A generalized linear model was used to find associations between covariates and a) sleep hours, and b) sleep weekend minus - weekdays. Results: We analyzed 577 children (median 9.5 y, 61% boys). Median bedtime was 22h. Median wake up time was 7h on weekdays and 9h on weekends. Median sleep duration was 9.5h during weekdays and 10h on weekends. The median difference in the amount of sleep during weekends and weekdays was 0.5h (IQR=1.5). Shorter sleep duration was associated with age and school schedule. Higher difference weekend - weekdays was associated with older children, girls, and school schedule. Conclusion: Children 7 to 13 years usually sleep more on weekends. Age, morning and full-time classes are associated with shorter sleep duration on weekdays and higher weekend-weekdays; girls sleep more during weekends.