Prevalence of underhydration among schoolchildren and their mothers from the city and municipality of Niepolomice and Cracow in Southern Poland.

Proper hydration is crucial for overall well-being. Insufficient water intake can disrupt homeostasis and lead to severe health issues. This observational study aimed to evaluate the prevalence of underhydration among mother-child pairs and to determine the effect of sociodemographic factors and nutritional status on underhydration. It utilized a questionnaire complemented by a urine osmolality test to assess hydration status. Underhydration was defined as an osmolality greater than 800 mOsm/kgH₂O. Two urine samples were collected from each child - one immediately after waking (first morning sample) and another at school in the afternoon - while only a first morning sample was requested from the mothers. Conducted between March and June 2018, the study involved 125 schoolchildren (77 boys and 48 girls) with a mean age of 10.25±1.63 years, and their 125 mothers with a mean age of 39.89±4.49 years, residing in the city and municipality of Niepolomice and Cracow (southern Poland). The urine osmolality tests revealed underhydration in 49.2% of children in the morning and in 51% during school hours. Statistical analysis of risk factors for underhydration in children did not reveal any significant associations with place of residence, age, sex, body mass index (BMI), and waist-to-height-ratio (WHtR). Among the mothers, 23.7% showed signs of underhydration. A significant association was observed between underhydration and mothers BMI (OR 4.42; 95% CI: 1.73-11.32), with those who were overweight or obese facing a more than fourfold higher risk of underhydration compared to those of normal weight. A significant positive association in morning urine osmolality (rSp=0.364; p=0.013) was observed exclusively in mother-daughter pairs, suggesting that daughters may mirror their mothers' hydration behaviors. This study highlights the importance of initiatives to enhance water intake among both children and their mothers, especially those with excess body weight.