TC). Quantitative variables were analyzed using the Mann‐Whitney test or Student’s t‐test as appropriate. Qualitative variables were analyzed using the chi‐squared test. All statistical analyses were performed using SigmaStat® for Windows® (release 3.5 ‐ SPSS Inc., San Rafael, United States) and statistical learn more significance was set at p < 0.05. A total of 370 children were studied, of whom 167 were boys (45%) and 203 were girls (55%). There was a prevalence of 10% overweight (n = 38) and 8% obesity (n = 30). There was no statistically significant difference in the prevalence of excess weight between females and males (p = 0.6). The practice of regular

physical activity was observed in only 27% of children, with no significant difference regarding gender or age. The number of hours devoted to watching television and playing computer or video games was also verified. There was no significant association between these parameters and the presence or absence of obesity in these children. These data are summarized in Table 1. The children slept an average of 9.7 hours. An inverse association was observed between sleep duration find more and the child’s age (r = ‐0.4, p < 0.001). While 47% of children aged between 6 and 8 years slept more than ten hours a day, only 9% of children older than 10 years had this sleep duration profile (p < 0.001) (Fig. 1). No significant

association was observed between sleep duration and other variables, such as gender or regular physical activity. Regarding the association between sleep duration and obesity, there was a tendency for a higher prevalence of excess Bay 11-7085 weight among children who slept less than nine hours (23%), when compared with children who slept more than 10 hours (16%, p = 0.06). Moreover, there was a significant association between sleep duration and the circumferences that represent central

fat distribution: neck circumference (r = ‐0.1; p = 0.01) and waist circumference (r = ‐0.2; p < 0.001). However, these associations were not independent from the association between sleep duration and age, when analyzed by multiple linear regressions. The genotype distribution regarding the 3111 T/C polymorphism of the CLOCK gene was 4% of children homozygous for the C allele (n = 13), 31% heterozygous (n = 106), and 65% homozygous for the T allele (n = 221); which is consistent with the Hardy‐Weinberg equilibrium (P = 0.98). Although both the prevalence of excess weight (31%) and the median BMI Z‐score were greater in individuals homozygous for the C allele, this difference did not show statistical significance. Likewise, no significant difference was observed regarding sleep duration in children classified in the different genotype groups (Table 2). Sleep duration has been decreasing in parallel with the increased incidence of obesity.