Urine osmolality among elementary school children living in a hot climate: Implications for dehydration

Objectives. Long-term dehydration may increase the risk for nephrolithiasis. It may also adversely affect mental abilities. The aim of our study was to determine the prevalence of voluntary dehydration among elementary school children in a semi-arid area in southern Israel, populated by two different ethnic groups (Jews and Bedouins). Methods. The osmolality and electrolyte content of urine samples obtained from 354 elementary school children, aged 8-10 years, were determined. Results. The osmolality of urine obtained at midday was high, exceeding 800 mosm/kg H₂O in 72.6% of children, but was significantly higher among Jews compared with Bedouins (906 ± 183 vs 771 ± 196 mosm/kg respectively, p < 0.001). Mean urinary solute load was not different. Implications for practice. A high rate of voluntary dehydration was found among children in our area, which may have potential adverse consequences, both on the high known rate for urolithiasis in our area and on intellectual abilities.