Duração do sono e gordura corporal na adolescência.

Abstract

In the last years the influence of sleep duration on body composition has been widely studied. However, the findings are still inconclusive, especially those including adolescents. Thus, the aim of the present thesis was to conduct a systematic review on the influence of sleep duration on body composition, overweight and/or obesity in adolescents, to investigate factors associated with sleep duration in adolescence, and to assess the association between sleep duration trajectories from 11 to 18 years of age and body composition at 18 years. The study was conducted using data from the 1993 Pelotas Birth Cohort, in Brazil. At the age of 18, 4563 adolescents were located. Of these, 4106 were interviewed (follow-up rate 81.3%). In the analysis, 4085 and 3974 adolescents were included with complete data on sleep duration and body composition, respectively. Sleep duration was assessed by asking the adolescents the time they usually fall asleep and wake up on weekdays. Body composition (fat mass and fat-free mass) was obtained by air displacement plethysmography (BOD POD®). In both original papers we performed crude and adjusted analyzes using Linear Regression. We observed that longer sleep duration at 18 years of age was associated with perinatal variables (low maternal schooling, low family income, maternal black skin colour, and low birth weight) and those collected at 18-year follow-up (being out of school, low school achievement, low family income, absence of depressive symptoms, and high screen time). Regarding the influence of sleep duration trajectories on adolescent body composition, we found association among girls only. Girls who improved their sleep duration from 11 to 18 years of age showed an increase in body mass, fat mass, and fatfree mass indices compared to those who always had adequate sleep duration. These results suggest that social and demographic variables may play an important role in determining adolescents sleep duration. Also, they show gender differences in the relationship between sleep duration and body composition.