title: First report on the association of drinking water hardness and endothelial function in children and adolescents.
abstract: BACKGROUND
  This study aims to investigate the relationship of water hardness and its calcium and magnesium content with endothelial function in a population-based sample of healthy children and adolescents.
  
  
  METHODS
  This case-control study was conducted in 2012 among 90 individuals living in two areas with moderate and high water hardness in Isfahan County, Iran. The flow-mediated dilatation (FMD) of the brachial artery and the serum levels of soluble adhesion molecules (sICAM-1, sVCAM-1) were measured as surrogate markers of endothelial function, and high-sensitivity C-reactive protein (hs-CRP), as a marker of inflammation.
  
  
  RESULTS
  Data of 89 participants (51% boys, mean age 14.75 (2.9) years) were complete. Those participants living in the area with high water hardness had higher FMD, hs-CRP, and soluble adhesion molecules (sICAM-1, sVCAM-1) than their counterparts living in the area with moderate water hardness. Multiple linear regression analysis showed that after adjustment for confounding factors of age, gender, body mass index, healthy eating index and physical activity level, total water hardness, as well as water content of calcium and magnesium, had a significant positive relationship with FMD. The corresponding associations were inverse and significant with soluble adhesion molecules (p < 0.05).
  
  
  CONCLUSIONS
  This study, which to the best of our knowledge is the first of its kind in the pediatric age group, suggests that water hardness, as well as its calcium and magnesium content, may have a protective role against early stages of atherosclerosis in children and adolescents.
authors.affiliation: Environment Research Center, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Parinaz
authors.initials: P
authors.lastname: Poursafa
authors.affiliation: Child Growth and Development Research Center, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Roya
authors.initials: R
authors.lastname: Kelishadi
authors.affiliation: Environment Research Center, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Mohammad Mehdi
authors.initials: MM
authors.lastname: Amin
authors.affiliation: Cardiology Department, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Hashemi
authors.affiliation: Dehaghan Health Center, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Maryam
authors.initials: M
authors.lastname: Amin
keywords: calcium; children and adolescents; endothelial function; magnesium; water hardness