title: A combination of low serum concentrations of vitamins K1 and D is associated with increased risk of hip fractures in elderly Norwegians: a NOREPOS study.
abstract: The present study investigated the risk of incident hip fractures according to serum concentrations of vitamin K1 and 25-hydroxyvitamin D in elderly Norwegians during long-term follow-up. The results showed that the combination of low concentrations of both vitamin D and K1 provides a significant risk factor for hip fractures.
  
  
  BACKGROUND
  This case-cohort study aims to investigate the associations between serum vitamin K1 and hip fracture and the possible effect of 25-hydroxyvitamin D (25(OH)D) on this association.
  
  
  METHODS
  The source cohort was 21,774 men and women aged 65 to 79 years who attended Norwegian community-based health studies during 1994-2001. Hip fractures were identified through hospital registers during median follow-up of 8.2 years. Vitamins were determined in serum obtained at baseline in all hip fracture cases (n = 1090) and in a randomly selected subcohort (n = 1318). Cox proportional hazards regression with quartiles of serum vitamin K1 as explanatory variable was performed. Analyses were further performed with the following four groups as explanatory variable: I: vitamin K1 ≥ 0.76 and 25(OH)D ≥ 50 nmol/l, II: vitamin K1 ≥ 0.76 and 25(OH)D < 50 nmol/l, III: vitamin K1 < 0.76 and 25(OH)D ≥ 50 nmol/l, and IV: vitamin K1 < 0.76 and 25(OH)D < 50 nmol/l.
  
  
  RESULTS
  Age- and sex-adjusted analyses revealed an inverse association between quartiles of vitamin K1 and the risk of hip fracture. Further, a 50 % higher risk of hip fracture was observed in subjects with both low vitamin K1 and 25(OH)D compared with subjects with high vitamin K1 and 25(OH)D (HR 1.50, 95 % CI 1.18-1.90). The association remained statistically significant after adjusting for body mass index, smoking, triglycerides, and serum α-tocopherol. No increased risk was observed in the groups low in one vitamin only.
  
  
  CONCLUSIONS
  Combination of low concentrations of vitamin K1 and 25(OH)D is associated with increased risk of hip fractures.
authors.affiliation: Department of Internal Medicine, Innlandet Hospital Trust, Skolegata 32, N-2318, Hamar, Norway. trine_finnes@yahoo.com.|Institute of Health and Society, Faculty of Medicine, University of Oslo, Oslo, Norway. trine_finnes@yahoo.com.
authors.forename: T E
authors.initials: TE
authors.lastname: Finnes
authors.affiliation: Department of Endocrinology, Oslo University Hospital, Oslo, Norway.
authors.forename: C M
authors.initials: CM
authors.lastname: Lofthus
authors.affiliation: Institute of Health and Society, Faculty of Medicine, University of Oslo, Oslo, Norway.|Division of Epidemiology, Norwegian Institute of Public Health, Oslo, Norway.
authors.forename: H E
authors.initials: HE
authors.lastname: Meyer
authors.affiliation: Division of Epidemiology, Norwegian Institute of Public Health, Oslo, Norway.
authors.forename: A J
authors.initials: AJ
authors.lastname: Søgaard
authors.affiliation: Department of Global Public Health and Primary Care, University of Bergen, Bergen, Norway.
authors.forename: G S
authors.initials: GS
authors.lastname: Tell
authors.affiliation: Department of Global Public Health and Primary Care, University of Bergen, Bergen, Norway.|Department of Rheumatology, Haukeland University Hospital, Bergen, Norway.
authors.forename: E M
authors.initials: EM
authors.lastname: Apalset
authors.affiliation: Department of Rheumatology, Haukeland University Hospital, Bergen, Norway.|Department of Clinical Science, University of Bergen, Bergen, Norway.
authors.forename: C
authors.initials: C
authors.lastname: Gjesdal
authors.affiliation: Department of Clinical Medicine, Arctic University of Norway, Tromsø, Norway.|Division of Internal Medicine, University Hospital of North Norway, Tromsø, Norway.
authors.forename: G
authors.initials: G
authors.lastname: Grimnes
authors.affiliation: Department of Public Health and General Practice Norwegian, University of Science and Technology, Trondheim, Norway.
authors.forename: B
authors.initials: B
authors.lastname: Schei
authors.affiliation: Department of Nutrition, Faculty of Medicine, University of Oslo, Oslo, Norway.|Division of Cancer Medicine, Surgery and Transplantation, Oslo University Hospital, Oslo, Norway.
authors.forename: R
authors.initials: R
authors.lastname: Blomhoff
authors.affiliation: Division of Epidemiology, Norwegian Institute of Public Health, Oslo, Norway.|Department of Mathematics, University of Oslo, Oslo, Norway.
authors.forename: S O
authors.initials: SO
authors.lastname: Samuelsen
authors.affiliation: Division of Epidemiology, Norwegian Institute of Public Health, Oslo, Norway.
authors.forename: K
authors.initials: K
authors.lastname: Holvik
mesh_terms: D000368:Aged; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006620:Hip Fractures / Q000097:blood / Q000453:epidemiology / Q000209:etiology*; D006801:Humans; D008297:Male; D009664:Norway / Q000453:epidemiology; D012307:Risk Factors; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D014808:Vitamin D Deficiency / Q000097:blood / Q000150:complications* / Q000453:epidemiology; D010837:Vitamin K 1 / Q000097:blood*; D014813:Vitamin K Deficiency / Q000097:blood / Q000150:complications* / Q000453:epidemiology
chemical_list: D014807:Vitamin D; D010837:Vitamin K 1; C104450:25-hydroxyvitamin D
keywords: Case cohort; Elderly; Hip fracture; Osteoporosis; Vitamin D; Vitamin K1