title: Low serum levels of 25-hydroxyvitamin D predict hip fracture in the elderly: a NOREPOS study.
abstract: BACKGROUND
  Despite considerable interest, the relationship between circulating 25-hydroxyvitamin D and the risk of hip fracture is not fully established.
  
  
  OBJECTIVE
  The objective of the study was to study the association between serum 25-hydroxyvitamin D concentrations [s-25(OH)D] and the risk of hip fracture in Norway, a high-latitude country that has some of the highest hip fracture rates worldwide.
  
  
  METHODS
  A total of 21 774 men and women aged 65-79 years attended 4 community-based health studies during 1994-2001. Information on subsequent hip fractures was retrieved from electronic hospital discharge registers, with a maximum follow-up of 10.7 years. Using a stratified case-cohort design, s-25(OH)D was determined by HPLC-atmospheric pressure chemical ionization-mass spectrometry in stored serum samples in hip fracture cases (n = 1175; 307 men, 868 women) and in gender-stratified random samples (n = 1438). Cox proportional hazards regression adapted for the case-cohort design was performed.
  
  
  RESULTS
  We observed an inverse association between s-25(OH)D and hip fracture; those with s-25(OH)D in the lowest quartile (<42.2 nmol/L) had a 38% [95% confidence interval (CI) 9-74%] increased risk of hip fracture compared with the highest quartile (≥67.9 nmol/L) in a model accounting for age, gender, study center, and body mass index. The association was stronger in men than in women: hazard ratio 1.65 (95% CI 1.04-2.61) vs hazard ratio 1.25 (95% CI 0.95-1.65).
  
  
  CONCLUSIONS
  In this prospective case-cohort study of hip fractures, the largest ever reported, we found an increased risk of hip fracture in subjects in the lowest compared with the highest quartile of serum 25-hydroxyvitamin D. In accordance with the findings of previous community-based studies, low vitamin D status was a modest risk factor for hip fracture.
authors.affiliation: Department of Public Health and Primary Health Care, Institute of Medicine, University of Bergen, 5020 Bergen, Norway. kristin.holvik@fhi.no
authors.forename: Kristin
authors.initials: K
authors.lastname: Holvik
authors.forename: Luai A
authors.initials: LA
authors.lastname: Ahmed
authors.forename: Siri
authors.initials: S
authors.lastname: Forsmo
authors.forename: Clara G
authors.initials: CG
authors.lastname: Gjesdal
authors.forename: Guri
authors.initials: G
authors.lastname: Grimnes
authors.forename: Sven Ove
authors.initials: SO
authors.lastname: Samuelsen
authors.forename: Berit
authors.initials: B
authors.lastname: Schei
authors.forename: Rune
authors.initials: R
authors.lastname: Blomhoff
authors.forename: Grethe S
authors.initials: GS
authors.lastname: Tell
authors.forename: Haakon E
authors.initials: HE
authors.lastname: Meyer
mesh_terms: D000368:Aged; D015331:Cohort Studies; D005260:Female; D006620:Hip Fractures / Q000097:blood* / Q000453:epidemiology / Q000209:etiology; D006801:Humans; D015994:Incidence; D008297:Male; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012306:Risk; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D