title: Distribution and correlates of serum 25-hydroxyvitamin D levels in a sample of patients with hip fracture.
abstract: BACKGROUND
  Vitamin D deficiency is common in older populations, particularly during the winter months due to low levels of ultraviolet light exposure, and in nursing home residents.
  
  
  OBJECTIVE
  The main objective of the current study was to assess the distribution of serum 25-hydroxyvitamin D and its correlates in a sample of men and women with recent hip fractures who were part of a large clinical trial.
  
  
  METHODS
  This was a cross-sectional exploratory study of screened and ultimately randomized patients with hip fractures. They were part of a multinational (115 clinical centers in 20 countries), randomized, placebo-controlled, double-blind study testing the efficacy of a yearly IV bisphosphonate (zoledronic acid) in the prevention of new clinical fractures in patients with recent hip fracture repair. Levels of 25-hydroxyvitamin D, calcium, alkaline phosphatase, creatinine clearance, and albumin were measured at a screening visit using blood serum. Demographic variables were assessed by patient self-report. Bone mineral density (BMD) was assessed by dual-energy x-ray absorptiometry of the nonfractured hip.
  
  
  RESULTS
  This report included 1174 screened patients (526 with vitamin D measured) and 655 (385 with vitamin D measured) patients randomized before the protocol amendment. In screened patients, levels of 25-hydroxyvitamin D were low (median, 14.7 ng/mL; interquartilc range, 7.6, 21.65). Overall, 51% were at or below the clinically meaningful threshold of 15 ng/mL. Among those patients randomized, the level of 25-hydroxyvitamin D was significantly positively related to male sex (rho, 0.13; P < 0.05), serum calcium (rho, 0.16; P < 0.01), and BMD at the femoral neck (rho, 0.22; P < 0.01) in bivariate analyses. Low serum 25-hydroxyvitamin D (<15 ng/mL) was related only to low serum calcium (odds ratio, 0.16; 95% CI, 0.05-0.52) in multivariable logistic models controlling for sex, age, race, body mass index, living at home, alkaline phosphatase, and creatinine clearance.
  
  
  CONCLUSIONS
  We concluded that vitamin D insufficiency was a common problem in this population of elderly patients who had recently suffered a hip fracture. This insufficiency was related only to serum calcium in multivariable controlled models but cannot be reliably identified or excluded by measuring serum calcium alone. Physicians should be encouraged to check and monitor patients' serum levels of 25-hydroxyvitamin D.
authors.affiliation: Center on Aging and Human Development, Duke University Medical Center, Durham, North Carolina 27710, USA. carl.pieper@duke.edu
authors.forename: Carl F
authors.initials: CF
authors.lastname: Pieper
authors.forename: Cathleen
authors.initials: C
authors.lastname: Colon-Emeric
authors.forename: John
authors.initials: J
authors.lastname: Caminis
authors.forename: Kathleen
authors.initials: K
authors.lastname: Betchyk
authors.forename: Jie
authors.initials: J
authors.lastname: Zhang
authors.forename: Cheri
authors.initials: C
authors.lastname: Janning
authors.forename: John
authors.initials: J
authors.lastname: Shostak
authors.forename: Meryl S
authors.initials: MS
authors.lastname: LeBoff
authors.forename: Robert R
authors.initials: RR
authors.lastname: Heaney
authors.forename: Kenneth W
authors.initials: KW
authors.lastname: Lyles
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015519:Bone Density; D050071:Bone Density Conservation Agents / Q000627:therapeutic use; D002118:Calcium / Q000097:blood*; D003430:Cross-Sectional Studies; D004164:Diphosphonates / Q000627:therapeutic use; D004311:Double-Blind Method; D005260:Female; D005272:Femur Neck / Q000378:metabolism; D006620:Hip Fractures; D006801:Humans; D007093:Imidazoles / Q000627:therapeutic use; D016015:Logistic Models; D008297:Male; D015999:Multivariate Analysis; D012737:Sex Factors; D014018:Tissue Distribution; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D000077211:Zoledronic Acid
chemical_list: D050071:Bone Density Conservation Agents; D004164:Diphosphonates; D007093:Imidazoles; D014807:Vitamin D; D000077211:Zoledronic Acid; C104450:25-hydroxyvitamin D; D002118:Calcium