title: Vitamin D in youth with Type 1 diabetes: prevalence of insufficiency and association with insulin resistance in the SEARCH Nutrition Ancillary Study.
abstract: OBJECTIVE
  To determine the prevalence of plasma vitamin D (25-dihydroxyvitamin D) insufficiency in individuals with Type 1 diabetes and to determine the cross-sectional and longitudinal associations of plasma vitamin D with insulin resistance.
  
  
  METHODS
  Participants from the SEARCH for Diabetes in Youth Study [n = 1426; mean age 11.2 years (sd 3.9)] had physician-diagnosed Type 1 diabetes [diabetes duration mean 10.2 months (sd 6.5)] with data available at baseline and follow-up (approximately 12 and 24 months after baseline). Insulin resistance was estimated using a validated equation. Cross-sectional and longitudinal multivariate logistic regression models were used to determine the association of plasma vitamin D with insulin resistance, adjusting for potential confounders.
  
  
  RESULTS
  Forty-nine per cent of individuals had plasma vitamin D < 50 nmol/l and 26% were insulin resistant. In cross-sectional multivariate analyses, participants who had higher plasma vitamin D (65 nmol/l) had lower odds of prevalent insulin resistance than participants with lower plasma vitamin D (25 nmol/l) (odds ratio 0.70, 95% CI 0.57-0.85). This association was attenuated after additional adjustment for BMI z-score, which could be a confounder or a mediator (odds ratio 0.81, 95% CI 0.64-1.03). In longitudinal multivariate analyses, individuals with higher plasma vitamin D at baseline had lower odds of incident insulin resistance, but this was not significant (odds ratio 0.85, 95% CI 0.63-1.14).
  
  
  CONCLUSIONS
  Vitamin D insufficiency is common in individuals with Type 1 diabetes and may increase risk for insulin resistance. Additional prospective studies are needed to determine the association between plasma vitamin D and insulin resistance, and to further examine the role of adiposity on this association.
authors.affiliation: Department of Health Sciences, Furman University, Greenville, SC.
authors.forename: N S
authors.initials: NS
authors.lastname: The
authors.forename: J L
authors.initials: JL
authors.lastname: Crandell
authors.forename: J M
authors.initials: JM
authors.lastname: Lawrence
authors.forename: I B
authors.initials: IB
authors.lastname: King
authors.forename: D
authors.initials: D
authors.lastname: Dabelea
authors.forename: S M
authors.initials: SM
authors.lastname: Marcovina
authors.forename: R B
authors.initials: RB
authors.lastname: D'Agostino
authors.forename: J M
authors.initials: JM
authors.lastname: Norris
authors.forename: C
authors.initials: C
authors.lastname: Pihoker
authors.forename: E J
authors.initials: EJ
authors.lastname: Mayer-Davis
mesh_terms: D000293:Adolescent; D002648:Child; D003922:Diabetes Mellitus, Type 1 / Q000209:etiology*; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D007333:Insulin Resistance / Q000502:physiology; D008297:Male; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D014808:Vitamin D Deficiency / Q000150:complications*; D055815:Young Adult
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D
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