Physical activity and sedentary behavior impacts on dietary water intake and hydration status in Spanish schoolchildren: A cross-sectional study

Background The importance of maintaining an adequate hydration status and the complexity of the water balance make it necessary to study the lifestyle factors that can influence or modify these variables. The aim of this study was to evaluate the hydration status and dietary water intake for a sample of Spanish schoolchildren from 7 to 12 years old and their associations with physical activity (PA) and sedentary behaviors. Methods A total of 242 schoolchildren was studied (49.17% females). A 24-hour urine sample was collected from each child, and the urine volume and osmolality were measured to estimate the hydration status (adequate hydration <= 800 mOsm/kg). In addition, a 3-day dietary record was completed to evaluate their water intake according to EFSA parameters. Dietary information was processed with DIAL software, and a statistical analysis was performed using SPSS. Student's t-test was used to study the normal variables, and the Mann-Whitney U test was used for those that were not normal. In the case of the categorical variables, the Z and Chi-Square proportions tests were used. The Bonferroni test was used to adjust the values in multiple comparisons. To evaluate the influence of these lifestyles on the urine osmolality, a 2-way ANOVA and an odds ratio were used. Results A total of 48.3% of the sample presented an adequate hydration status, and the percentage was significantly higher in females (p = 0.003). Only 20.9% showed an adequate intake of dietary water. The lifestyle influence reveals that more inactive and non-sedentary schoolchildren were adequately hydrated (p = 0.008). PA (practice >= 1 h/day) was associated with a higher risk of having an inadequate hydration status, even when accounting for sex and other lifestyle factors (OR = 1.753(1.006-3.054), p = 0.048). Conclusions Approximately half of the participants presented an inadequate hydration status (which was higher in males than in females). PA (practice >= 1 h/day) was associated with a higher risk of inadequate hydration. This fact highlighted the importance of raising awareness about hydration in children, especially in ones who are more active.