title: Vitamin K1 and 25(OH)D are independently and synergistically associated with a risk for hip fracture in an elderly population: a case control study.
abstract: OBJECTIVE
  The incidence of hip fractures in Oslo is among the highest in the world. Vitamin D, as well as vitamin K, may play an important role in bone metabolism. We examined if vitamin K1 and 25(OH)D were associated with an increased risk of hip fracture, and whether the possible synergistic effect of these two micronutrients is mediated through bone turnover markers.
  
  
  METHODS
  Blood was drawn for vitamin K1, 25(OH)D, and the bone turnover marker osteocalcin upon admission for hip fracture and in healthy controls.
  
  
  RESULTS
  Vitamin K1 and 25(OH)D were independently associated with a risk of hip fracture. The adjusted odds ratio (95% CI) per ng/ml increase in vitamin K1 was 0.07 (0.02-0.32), and that per nmol/L increase in 25(OH)D was 0.96 (0.95-0.98). There was a significant interaction between 25(OH)D and vitamin K1 (p < 0.001), and a significant correlation between total osteocalcin and vitamin K1 and 25(OH)D (rho = 0.18, p = 0.01; rho = 0.20, p = 0.01, respectively).
  
  
  CONCLUSIONS
  Vitamin K1 and 25(OH)D are lower in hip fracture patients compared with controls. Vitamin K1 and 25(OH)D are independently and synergistically associated with the risk of hip fracture when adjusting for confounders. Intervention studies should include both vitamins.
authors.affiliation: Oslo University Hospital, Oslo, Norway; Department of General Internal Medicine, Oslo, Norway. Electronic address: a.c.torbergsen@medisin.uio.no.
authors.forename: Anne C
authors.initials: AC
authors.lastname: Torbergsen
authors.affiliation: Oslo University Hospital, Oslo, Norway; Department of Geriatric Medicine, Oslo, Norway.
authors.forename: Leiv O
authors.initials: LO
authors.lastname: Watne
authors.affiliation: Oslo University Hospital, Oslo, Norway; Department of Geriatric Medicine, Oslo, Norway; Institute of Clinical Medicine, University of Oslo, Norway.
authors.forename: Torgeir B
authors.initials: TB
authors.lastname: Wyller
authors.affiliation: Oslo University Hospital, Oslo, Norway; Department of Orthopedic Medicine, Oslo, Norway.
authors.forename: Frede
authors.initials: F
authors.lastname: Frihagen
authors.affiliation: Oslo University Hospital, Oslo, Norway; Department of Orthopedic Medicine, Oslo, Norway; Institute of Clinical Medicine, University of Oslo, Norway.
authors.forename: Knut
authors.initials: K
authors.lastname: Strømsøe
authors.affiliation: Oslo University Hospital, Oslo, Norway; Department of Biochemistry, Nutrition Laboratory, Oslo, Norway; Institute of Clinical Medicine, University of Oslo, Norway.
authors.forename: Thomas
authors.initials: T
authors.lastname: Bøhmer
authors.affiliation: Oslo University Hospital, Oslo, Norway; Department of General Internal Medicine, Oslo, Norway; Institute of Clinical Medicine, University of Oslo, Norway.
authors.forename: Morten
authors.initials: M
authors.lastname: Mowe
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D016723:Bone Remodeling / Q000502:physiology; D016022:Case-Control Studies; D004357:Drug Synergism; D005260:Female; D006620:Hip Fractures / Q000453:epidemiology* / Q000209:etiology; D006801:Humans; D016015:Logistic Models; D008297:Male; D009664:Norway / Q000453:epidemiology; D016017:Odds Ratio; D015675:Osteocalcin / Q000097:blood; D012307:Risk Factors; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D010837:Vitamin K 1 / Q000097:blood*
chemical_list: D015675:Osteocalcin; D014807:Vitamin D; D010837:Vitamin K 1; C104450:25-hydroxyvitamin D
keywords: 25(OH)D; Bone markers; Hip fracture; Osteocalcin; Risk factors; Vitamin K1