Prevalence of voluntary dehydration according to urine osmolarity in elementary school students in the metropolitan region of São Paulo, Brazil

Abstract

OBJECTIVES:To evaluate the prevalence of voluntary dehydration based on urine osmolarity in elementary school students from two public educational institutions in the metropolitan region of São Paulo and evaluate whether there is a relationship between voluntary dehydration and nutritional status or socioeconomic status.METHODS:Analytical cross-sectional study with students from two public schools in the city of Osasco. The determination of urine osmolarity was performed using the freezing method of the Advanced® Osmometer Model 3W2. Urine osmolarity greater than 800 mOsm/kg H2O was considered voluntary dehydration. During data collection, the weights and heights of the students, environmental temperatures and air humidity levels were obtained.RESULTS:A total of 475 students aged six to 12 years were evaluated, of whom 188 were male. Voluntary dehydration occurred in 63.2% of the students and was more frequent in males than in females. The prevalence of voluntary dehydration was more frequent in males aged six to nine years than in females. However, no statistically significant difference was observed between males and females aged 10 to 12 years. No association was found between voluntary dehydration and nutritional status or socioeconomic status.CONCLUSION:The prevalence of voluntary dehydration was high in elementary school students and was more frequent in males. No association was found between voluntary dehydration and nutritional or socioeconomic status.

A Portable Biodevice to Monitor Salivary Conductivity for the Rapid Assessment of Fluid Status

“…As such, they are only moderately correlated with serum osmolality during acute dehydration. The current consensus considers urine osmolality a valid biomarker for diagnosing dehydration [ 24 , 25 , 26 ].…”

Hypohydration, Functional Constipation, and Physical Activity in Elementary School Students

“…Further investigations are also necessary to clarity the relationship between hypohydration and constipation, because constipation is a public health problem (1) and the prevalence of hypohydration is high in the pediatric population worldwide (8), as exemplified in Brazil (63.2%) (9).…”

“…Hypohydration was defined as urine osmolality >800 mOsm/ kg H 2 O (8)(9)(10)(11). A spot urine sample was collected from each participant in a sterile vial and stored at −20 ℃.…”

“…Low fluid intake may lead to hypohydration, also known as voluntary dehydration (5,(8)(9)(10)(11). The prevalence of hypohydration in children varies between 33% and 84% in studies conducted in several countries (8), including Brazil (9). Hypohydration increases vasopressin secretion, decreases urine production, and increases urinary osmolality (10).…”

Change in Metabolomic Profile Associated with an Average Increase in Plain Water Intake of >+1 L/Day, Sustained Over 4 Weeks, in Healthy Young Men with Initial Total Water Intake Below 2 L/Day

“…The present analysis focused on study participants who changed hydration classification. Between Week 1 and Week 6, urine osmolality decreased below 800 mOsm/kg H 2 O, saliva osmolality decreased below 100 mOsm/kg H 2 O, and serum osmolality remained below 295 mOsm/kg H 2 O. Urine osmolality of 800 mOsm/kg H 2 O or higher is frequently interpreted as suboptimal hydration, underhydration, or index of hyperosmotic stress on cells (cell dehydration) [108][109][110][111][112]. Saliva osmolality above 100 mOsm/kg H 2 O approximately corresponds with a total body water (TBW) deficit greater than 1% [113,114].…”