title: Belgian primary school children's hydration status at school and its personal determinants.
abstract: OBJECTIVE
  Dehydration has been related to several health aspects, and children are especially vulnerable. Since children spend a large time at school, we aim to examine children's hydration status at school-start and its change during the school-day by objective measures. To identify subpopulations at risk, determinants of hydration were tested.
  
  
  METHODS
  In 371 Belgian 7-13-year-old children, hydration was measured by (1) urinary osmolality at school-start and by a pooled school-day sample; (2) body water% by impedance; (3) parental reported beverage consumption; (4) urination frequency. Linear regression analyses were used to test putative predictors of hydration status: age, sex, parental education, region (Dutch-speaking versus French-speaking part of Belgium), diet quality and adiposity.
  
  
  RESULTS
  A mean osmolality of 888 mosmol/kg was found in the school-start sample and 767 mosmol/kg in the school-day sample. This resulted in, respectively, 76 and 54 % of the children being dehydrated (>800 mosmol/kg). In 45 % of the children, the hydration level decreased over the school-day. Also the body water% as derived from bio-impedance (57 % ±4), the reported average daily beverage intake (911 ml) and the lower urination frequency during weekdays versus weekend days confirmed the low hydration status in our school population. Boys, Walloon children and those with higher adiposity were at increased risk of low hydration level. Diet quality was not the predictor of hydration status.
  
  
  CONCLUSIONS
  Hydration status at school appeared problematic in this population. This emphasizes the need for more resources and attention by school management and governmental organizations. Herein, especially Walloon schools and boys should be reached.
authors.affiliation: Department of Public Health, Faculty of Medicine and Health Sciences, Ghent University, De Pintelaan 185, 4K3, 9000, Ghent, Belgium. Nathalie.michels@ugent.be.
authors.forename: Nathalie
authors.identifier: http://orcid.org/0000-0002-3069-7254
authors.initials: N
authors.lastname: Michels
authors.affiliation: Department of Public Health, Faculty of Medicine and Health Sciences, Ghent University, De Pintelaan 185, 4K3, 9000, Ghent, Belgium.
authors.forename: Karen
authors.initials: K
authors.lastname: Van den Bussche
authors.affiliation: Department of Pediatric Nephrology/Urology, University Hospital Ghent, De Pintelaan 185, 9000, Ghent, Belgium.
authors.forename: Johan
authors.initials: J
authors.lastname: Vande Walle
authors.affiliation: Department of Public Health, Faculty of Medicine and Health Sciences, Ghent University, De Pintelaan 185, 4K3, 9000, Ghent, Belgium.|Department of Health Sciences, Vesalius, University College Ghent, Keramiekstraat 80, 9000, Ghent, Belgium.
authors.forename: Stefaan
authors.initials: S
authors.lastname: De Henauw
mesh_terms: D050154:Adiposity; D000293:Adolescent; D017195:Adolescent Nutritional Physiological Phenomena / Q000208:ethnology; D001530:Belgium / Q000453:epidemiology; D001628:Beverages / Q000009:adverse effects; D015415:Biomarkers / Q000652:urine; D001834:Body Water; D002648:Child; D002664:Child Nutritional Physiological Phenomena / Q000208:ethnology; D003681:Dehydration / Q000453:epidemiology / Q000208:ethnology / Q000209:etiology* / Q000652:urine; D004032:Diet / Q000009:adverse effects* / Q000208:ethnology; D005260:Female; D006801:Humans; D008297:Male; D009749:Nutrition Surveys; D009752:Nutritional Status / Q000208:ethnology; D009994:Osmolar Concentration; D010290:Parents; D012306:Risk; D012574:Schools; D012737:Sex Factors; D014554:Urination
chemical_list: D015415:Biomarkers
keywords: Adiposity; Diet quality; Hydration; Sociodemographic; Urinary osmolality