Hydration status, total water intake and subjective feelings of adolescents living in a hot environment, during a typical school day.

Aim: Individuals living in a hot environment appear to face increased risk of dehydration. Currently there is not extensive literature on the adolescent population in relation to hydration. The aim of the present study was to assess hydration status and total water intake (TWI) at school, of adolescents living in a hot environment, and to investigate the association of hydration and TWI with various subjective feelings.

Methods: The hydration status of 141 adolescents (boys n = 102), age 15-17 years, was assessed via urine specific gravity (USG), at the beginning (07:30 am) and at the end (1:30 pm) of one school day. TWI from fluids and solid food was assessed via detailed food and fluid records. Subjective feelings (i.e. thirst, alertness, ability to concentrate) were recorded by specific scales.

Results: Ninety percent of the students arrived dehydrated at school (USG >1.020). Thirteen students were hydrated (USG <1.020), 67 students were slightly dehydrated (USG 1.021-1.029), and 50 students were seriously dehydrated (USG >1.030). There was no difference in TWI between the three groups (765 ± 451 mL). TWI correlated with alertness (p = 0.005) and the ability to concentrate (p = 0.015), and inversely correlated with fatigue (p = 0.015). Seriously dehydrated students felt less alert in the morning (p < 0.035) whereas the feeling of thirst was similar between all groups.

Conclusions: The prevalence of the dehydration of the adolescents during school time appeared to be extremely high, and thirst was not driving those adolescents to drink enough. Apart from health concerns, school performance could be affected by dehydration and inadequate water intake.