Tempo de sono e variação do IMC em escolares: análise conjunta de seis ensaios randomizados de base escolar

Abstract

Children and adolescents have shown insufficient sleep leading to the risk of developing diseases. Cross-sectional studies show that few hours of sleep are associated with obesity, whereas in longitudinal studies, these results are inconclusive. The aim of this study is to analyze the relationship between inadequate sleep time (short and long) and BMI variation in schoolchildren. Data from 5 school-based randomized trials for obesity prevention, which took place from 2005 to 2019, lasted one school year, totaling 5369 schoolchildren, were used. Sleep time was assessed at baseline and categorized into short, adequate, and long sleep according to the cutoff points recommended by the American Academy of Sleep Medicine (2016). Longitudinal analysis with mixed effects was used, considering the cluster effect of schools, to verify the BMI variation rate over time according to sleep categories. Crude and adjusted analyses for possible confounding factors (gender, screen time, and race/color), were performed using the SAS software. Age in each study was used as the time indicator variable, and the models were additionally adjusted for the year of each study, with the objective of correcting the model for the increase in BMI with age. It was observed that 17.2% of students were overweight and 11.6% were obese. The frequency of adequate sleep was 60%, 31% of the students had a short sleep and 8.9% had long sleep. The mean age, weight, height and BMI were higher among those who had long sleep both at baseline (12.8; 47.1; 154.8 and 19.4, respectively) and at follow-up (13.2; 49.4; 156.8 and 19.8, respectively). However, the variation in BMI over time was not altered according to sleep time (p-value =0.93). The present study, involving longitudinal pooled analysis, did not identify an effect on the association between sleep time and BMI variation. Students with long sleep times had higher BMI at baseline and remained so throughout the observation.