title: The effect of voluntary dehydration on cognitive functions of elementary school children.
abstract: OBJECTIVE
  (1) To describe the occurrence of voluntary dehydration in two classes of elementary school students as expressed by their morning and noon-time urine osmolality; and (2) to determine the relationship between the children's scores on cognitive tests and their state of hydration.
  
  
  METHODS
  Group comparison among fifty-eight sixth-grade students (age range 10.1-12.4 y old) during mid-June at two schools in a desert town. Morning and noon-time urine samples were collected in school, and five cognitive tests were scored in the morning and at noon-time.
  
  
  METHODS
  (1) morning and noon-time urine osmolality; (2) scores of five cognitive tests (hidden figures, auditory number span, making groups, verbal analogies, and number addition) that were applied in the morning and at noon-time.
  
  
  RESULTS
  Thirty-two students were dehydrated (urine osmolality above 800 mosm/kg H(2)O) in the morning. An individual's noon-time urine osmolality was highly related to morning osmolality (r=0.67, p=0.000). The morning cognitive scores were similar in the hydrated and dehydrated students (p=0.443). The adjusted mean scores of the noon-time tests, with the morning test scores as covariates, demonstrated an overall positive trend in four of the five tests in favor of the hydrated group (p=0.025). The effect was mainly due to the auditory number span test (p=0.024).
  
  
  CONCLUSIONS
  Voluntary dehydration is a common phenomenon in school-aged children that adversely affects cognitive functions.
authors.affiliation: Primary Pediatrics Unit and the Division of Pediatrics, Soroka University Medical Center, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
authors.forename: Yair
authors.initials: Y
authors.lastname: Bar-David
authors.forename: Jacob
authors.initials: J
authors.lastname: Urkin
authors.forename: Ely
authors.initials: E
authors.lastname: Kozminsky
mesh_terms: D002648:Child; D003071:Cognition; D003681:Dehydration / Q000453:epidemiology / Q000523:psychology*; D004327:Drinking Behavior; D005260:Female; D006801:Humans; D007557:Israel / Q000453:epidemiology; D008297:Male; D015999:Multivariate Analysis; D009994:Osmolar Concentration; D015995:Prevalence; D013334:Students / Q000523:psychology*; D014556:Urine / Q000737:chemistry