title: Circulating 25-hydroxyvitamin D is associated with insulin resistance cross-sectionally but not longitudinally in older adults: The Cardiovascular Health Study.
abstract: BACKGROUND
  Despite extensive study, the role of vitamin D in insulin resistance and secretion remains unclear.
  
  
  OBJECTIVE
  To examine the cross-sectional and longitudinal relationships between 25-hydroxyvitamin D (25(OH)D) concentrations and indices of insulin resistance and secretion in older adults.
  
  
  RESULTS
  Among 2134 participants of the Cardiovascular Health Study who were free from cardiovascular disease, we measured serum 25(OH)D concentrations in samples collected in 1992-1993. We examined insulin resistance and secretion using Homeostasis Model Assessment (HOMA) estimates cross-sectionally and among 1469 participants who had repeated HOMA measures four years later (1996-1997). In cross-sectional analysis, each 10 ng/mL increment in 25(OH)D concentration was associated with a 0.09 lower adjusted HOMA-IR [95% CI (-0.17, -0.02), p=0.01]. However, baseline 25(OH)D concentrations were not associated with change in HOMA-IR over 4 years of follow up (p=0.48). 25(OH)D concentrations were not associated with insulin secretion, as determined by HOMA-β, in either cross-sectional or longitudinal analysis.
  
  
  CONCLUSIONS
  Circulating 25(OH)D concentrations are associated with lower insulin resistance in cross-sectional but not longitudinal analyses. Whether this reflects residual confounding in cross-sectional analyses or the short-term nature of the relationship between vitamin D and insulin sensitivity will require trials with repeated measures of these factors.
authors.affiliation: Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA. Electronic address: jdanzige@bidmc.harvard.edu.
authors.forename: John
authors.initials: J
authors.lastname: Danziger
authors.forename: Mary L
authors.initials: ML
authors.lastname: Biggs
authors.forename: Matt
authors.initials: M
authors.lastname: Niemi
authors.forename: Joachim H
authors.initials: JH
authors.lastname: Ix
authors.forename: Jorge R
authors.initials: JR
authors.lastname: Kizer
authors.forename: Luc
authors.initials: L
authors.lastname: Djoussé
authors.forename: Ian H
authors.initials: IH
authors.lastname: de Boer
authors.forename: David S
authors.initials: DS
authors.lastname: Siscovick
authors.forename: Bryan
authors.initials: B
authors.lastname: Kestenbaum
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Mukamal
mesh_terms: D050154:Adiposity; D000368:Aged; D000886:Anthropometry; D002318:Cardiovascular Diseases / Q000453:epidemiology; D003430:Cross-Sectional Studies; D015444:Exercise / Q000502:physiology; D005260:Female; D006801:Humans; D006887:Hydroxycholecalciferols / Q000097:blood*; D007249:Inflammation / Q000097:blood; D007328:Insulin / Q000378:metabolism; D007333:Insulin Resistance / Q000502:physiology*; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000097:blood / Q000378:metabolism; D012307:Risk Factors; D011795:Surveys and Questionnaires
chemical_list: D006887:Hydroxycholecalciferols; D007328:Insulin
keywords: 25(OH)D; 25-hydroxyvitamin D; BMI; Body mass index; CES-D; CHS; Cardiovascular Health Study; Center for Epidemiological Studies Depression; HOMA; Homeostasis Model Assessment; Insulin resistance; Vitamin D