title: Low serum 25-hydroxyvitamin D level and risk of upper respiratory tract infection in children and adolescents.
abstract: BACKGROUND
  Vitamin D may be important for immune function. Studies to date have shown an inconsistent association between vitamin D and infection with respiratory viruses. The purpose of this study was to determine if serum 25-hydroxyvitamin D (25(OH)D) was associated with laboratory-confirmed viral respiratory tract infections (RTIs) in children.
  
  
  METHODS
  Serum 25(OH)D levels were measured at baseline and children from Canadian Hutterite communities were followed prospectively during the respiratory virus season. Nasopharyngeal specimens were obtained if symptoms developed and infections were confirmed using polymerase chain reaction. The association between serum 25(OH)D and time to laboratory-confirmed viral RTI was evaluated using a Cox proportional hazards model.
  
  
  RESULTS
  Seven hundred forty-three children aged 3-15 years were followed between 22 December 2008 and 23 June 2009. The median serum 25(OH)D level was 62.0 nmol/L (interquartile range, 51.0-74.0). A total of 229 participants (31%) developed at least 1 laboratory-confirmed viral RTI. Younger age and lower serum 25(OH)D levels were associated with increased risk of viral RTI. Serum 25(OH)D levels <75 nmol/L increased the risk of viral RTI by 50% (hazard ratio [HR], 1.51; 95% confidence interval [CI], 1.10-2.07, P = .011) and levels <50 nmol/L increased the risk by 70% (HR, 1.67; 95% CI, 1.16-2.40, P = .006).
  
  
  CONCLUSIONS
  Lower serum 25(OH)D levels were associated with increased risk of laboratory-confirmed viral RTI in children from Canadian Hutterite communities. Interventional studies evaluating the role of vitamin D supplementation to reduce the burden of viral RTIs are warranted.
authors.affiliation: Division of Infectious Diseases, The Hospital for Sick Children, Toronto, Canada.
authors.forename: Michelle
authors.initials: M
authors.lastname: Science
authors.forename: Jonathon L
authors.initials: JL
authors.lastname: Maguire
authors.forename: Margaret L
authors.initials: ML
authors.lastname: Russell
authors.forename: Marek
authors.initials: M
authors.lastname: Smieja
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Walter
authors.forename: Mark
authors.initials: M
authors.lastname: Loeb
mesh_terms: D000293:Adolescent; D002170:Canada / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D015995:Prevalence; D011446:Prospective Studies; D012141:Respiratory Tract Infections / Q000453:epidemiology*; D018570:Risk Assessment; D044967:Serum / Q000737:chemistry; D014777:Virus Diseases / Q000453:epidemiology*; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D
keywords: cold; serum 25-hydroxyvitamin D; upper respiratory tract infection; vitamin D