title: Association of serum vitamin D levels with inflammatory response following hip fracture: the Baltimore Hip Studies.
abstract: BACKGROUND
  Vitamin D, known for its role in calcium homeostasis, may also regulate immune function. Whether vitamin D deficiency at the time of hip fracture is associated with the inflammatory response postfracture is not known.
  
  
  METHODS
  In a cohort from the Baltimore Hip Studies, women aged >or= 65 years were evaluated at baseline and 2, 6, and 12 months after hip fracture repair. Serum at baseline was analyzed for 25-hydroxyvitamin D [25(OH)D], and serum from all time points was analyzed for interleukin-6 (IL-6). Participants were divided into two groups based on their baseline 25(OH)D levels. Vitamin D deficiency was defined as a 25(OH)D level of <or= 15 ng/mL (<37.5 nmol/L). We examined IL-6 level as a function of vitamin D status using generalized estimating equations, adjusting for covariates.
  
  
  RESULTS
  Women deficient in vitamin D at baseline had higher IL-6 levels in the year postfracture (p=.02). On average, participants with low 25(OH)D levels had adjusted serum IL-6 levels that were 6.0 pg/mL (95% confidence interval [CI]: -6.7, 18.7 pg/mL), 11.9 pg/mL (95% CI: 3.5, 20.4), 13.1 pg/mL (95% CI: 4.6, 21.6), and 13.4 pg/mL (95% CI: 2.3, 24.5) higher at baseline, 2, 6, and 12 months after hip fracture, respectively.
  
  
  CONCLUSIONS
  Women with vitamin D deficiency at the time of hip fracture had higher serum IL-6 levels in the year after hip fracture. Whether the proinflammatory state of vitamin D deficiency explains the association of this deficiency with adverse outcomes in older adults warrants further study.
authors.affiliation: Division of Gerontology , Department of Epidemiology and Preventive Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA. rrmiller@epi.umaryland.edu
authors.forename: Ram R
authors.initials: RR
authors.lastname: Miller
authors.forename: Gregory E
authors.initials: GE
authors.lastname: Hicks
authors.forename: Michelle D
authors.initials: MD
authors.lastname: Shardell
authors.forename: Anne R
authors.initials: AR
authors.lastname: Cappola
authors.forename: William G
authors.initials: WG
authors.lastname: Hawkes
authors.forename: Janet A
authors.initials: JA
authors.lastname: Yu-Yahiro
authors.forename: Achsah
authors.initials: A
authors.lastname: Keegan
authors.forename: Jay
authors.initials: J
authors.lastname: Magaziner
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D005260:Female; D006620:Hip Fractures / Q000097:blood*; D006801:Humans; D007249:Inflammation / Q000209:etiology*; D015850:Interleukin-6 / Q000097:blood; D014807:Vitamin D / Q000031:analogs & derivatives / Q000097:blood*
chemical_list: D015850:Interleukin-6; D014807:Vitamin D; C104450:25-hydroxyvitamin D