Sleep, social behaviour and food consumption of schoolchildren of a large Brazilian city.

Objective: To explore the impact of inadequate sleep and associated factors on the social behaviour and food consumption of children and adolescents.
Design: Cross-sectional study.
Setting: Sleep information, social behaviour (Strengths and Difficulties Questionnaire), food consumption, demography, nutritional status, lifestyle, and biochemical tests were investigated.
Participants: School children in the 4th grade of the municipal school system of a large Brazilian city.
Results: Of a total of 797 schoolchildren, 50·9 % were female, with a median age of 9·7 (9·5-10·0) years old and an energy consumption of 7613·6 (5982·7-9766·2) kJ. It was determined that 31·6 % were overweight, and 76·8 % reported insufficient weekly practice of physical activity. A median of 9·6 (8·9-10·5) h of sleep (lower values on weekdays: 9·3 v. 10·5 h, P < 0·001) was recorded. In addition, 27 % of the individuals who experienced inadequate sleep (<9 h) engaged in longer screen time daily (≥2 h/d) (P = 0·05), had an inadequate bedtime (> 22 h) or adequate wake-up time (5-7 h), studied in the morning (P < 0·001) and never took a shower before school (P < 0·001). Of the entire sample, 9·9 % had poor or very poor sleep quality and a greater probability of sleep talking regularly, had difficulty falling asleep, and engaged in inadequate social behaviour while experiencing these conditions compared with those with positive sleep quality. There was no association between sleep and the other variables investigated.
Conclusions: Sleep impairment contributed to changes in sleep and social behaviour in schoolchildren. The findings of this study may reinforce the importance of developing actions to promote adequate sleep and a healthy lifestyle at school age.