Trajetórias de duração do sono, composição corporal e altura atingida na infância: Coorte de nascimentos de Pelotas de 2004

Abstract

The importance of sleep and biological rhythms has been recognized to maintain health and prevent diseases. Sleep duration has been studied as an essential factor concerning physical, mental, and behavioral issues. Evidence suggests that short sleep is a risk factor for overweight and obesity. However, few studies have evaluated its effects on children's body composition, including adipose tissue and lean mass. Some previous studies have also suggested that shorter sleep duration could be related to lower linear growth, but literature on this topic is scarce. Thus, the first objective of this thesis was to describe sleep duration trajectories among children participating in the 2004 Pelotas Birth Cohort. For this purpose, data on sleep duration from the 3, 12, 24, and 48 month follow-ups and socioeconomic, maternal, and children's characteristics were used to assess possible associated factors. Three sleep duration trajectories were identified using a semi-parametric, group-based modeling approach, called “short sleepers,” “typical sleepers,” and “initially longer sleepers”. Wh n compared to the “typical sleepers,” children from less schooled mothers (OR: 1.82; 95%CI: 1.26; 2.62), who claimed to have had depression or nervous problems during pregnancy (OR: 1.31; 95%CI: 1.02; 1.68) and who consumed alcoholic beverages at 3 months after delivery (OR: 1.60; 95%CI: 1.03; 2.50), as well as those children who shared the bedroom with another child at 3 months (OR: 1.41; 95%CI: 1.07; 1.87) presented higher odds to belong to the group of “short sleepers”. The objective of the review article was to locate the existing literature about longitudinal studies evaluating the association of sleep duration with body composition and dietary behaviors in children and adolescents. These behaviors have been considered as potential mediators of the relationship between shorter sleep duration and weight gain. The results of studies evaluating the relationship between sleep duration and body composition were controversial. Some studies have shown a greater accumulation of body fat in short sleepers, others null results and some have presented different directions regarding lean mass. In addition, few longitudinal studies have evaluated similar outcomes in the relationship between sleep duration and dietary behaviors. However, findings suggest that short sleep duration is related to higher energy consumption and unhealthy eating behaviors. Finally, the second original article was developed to investigate whether sleep duration trajectories were associated with anthropometric (including height) and body composition measurements, at 6 and 11 years of age, among children participating in the same cohort. In the unadjusted analysis, it was observed that children belonging to the "short sleepers" group presented lower height at 6 (β: -0.78; 95%CI: -1.42; -0.13) and 11 years (β: -1.07; 95%CI: -1.94; -0.21) and lower heightfor-age z-score at 6 (3: -0.16; 95%CI: -0.29; -0.04) and 11 years (β: -0.14; 95%CI: -0.27; -0.01), when compared to children in the "typical sleepers" group. Nevertheless, after adjusting for potential confounding factors, the associations disappeared. Thus, the sleep duration trajectories of children from 3 to 48 months of age were not associated with any of the anthropometric or body composition variables at 6 and 11 years of age.