title: Higher 1,25-dihydroxyvitamin D3 concentrations associated with lower fall rates in older community-dwelling women.
abstract: BACKGROUND
  The purpose of this study was to examine the relationships of vitamin D supplementation and serum concentrations of vitamin D metabolites and parathyroid hormone (PTH) with neuromuscular function and falls in older community-dwelling women.
  
  
  METHODS
  We examined these relationships using a 4-year prospective multi-center study among 9,526 community-dwelling women enrolled in the Study of Osteoporotic Fractures (median age: 70 years; interquartile range: 67-75) and a subset of 389 women (97%) out of 400 who were randomly selected from the entire cohort for serum measures. Measurements included: vitamin D supplementation, serum 25-hydroxyvitamin D(3) [25(OH)D(3)], serum 1,25-dihydroxyvitamin D(3) [1,25(OH) (2)D(3)], and serum intact parathyroid hormone (iPTH); grip and quadriceps strength, chair-stand time, walking speed, reaction time, and balance-walk time (including changes in grip strength, chair-stand time, walking speed and balance-walk time over approximately 3.7 years); and incident fall rates (number of falls/woman-years).
  
  
  RESULTS
  In 9,526 women, vitamin D supplementation was not associated with any measures of neuromuscular function, change in neuromuscular function, or fall rates (p>0.01 for all). In a subgroup of 389 women, there was a trend of higher 25(OH)D(3) concentration with slightly weaker grip strength (p=0.007), and women in the fourth quartile of 1,25(OH)(2)D(3) had a faster chair-stand time (p=0.017) than women in the first quartile; still, in general, concentrations of 25(OH)D(3), 1,25(OH)(2)D(3), and iPTH were not associated with either neuromuscular function or changes in neuromuscular function (p>0.05 for all). However, higher 1,25(OH)(2)D(3) concentration was associated with lower fall rates (p=0.039).
  
  
  CONCLUSIONS
  Higher 1,25(OH)(2)D(3) concentration is associated with a lower fall risk in older community-dwelling women, but vitamin D supplementation, and 25(OH)D(3) and iPTH concentrations are not associated with either neuromuscular function or falls.
authors.affiliation: University of Pittsburgh, 130 DeSoto Street, Parran 509, Pittsburgh, PA 15261, USA. kaf24@pitt.edu
authors.forename: K A
authors.initials: KA
authors.lastname: Faulkner
authors.forename: J A
authors.initials: JA
authors.lastname: Cauley
authors.forename: J M
authors.initials: JM
authors.lastname: Zmuda
authors.forename: D P
authors.initials: DP
authors.lastname: Landsittel
authors.forename: A B
authors.initials: AB
authors.lastname: Newman
authors.forename: S A
authors.initials: SA
authors.lastname: Studenski
authors.forename: M S
authors.initials: MS
authors.lastname: Redfern
authors.forename: K E
authors.initials: KE
authors.lastname: Ensrud
authors.forename: H A
authors.initials: HA
authors.lastname: Fink
authors.forename: N E
authors.initials: NE
authors.lastname: Lane
authors.forename: M C
authors.initials: MC
authors.lastname: Nevitt
mesh_terms: D000058:Accidental Falls / Q000706:statistics & numerical data*; D000368:Aged; D002117:Calcitriol / Q000097:blood*; D015331:Cohort Studies; D019587:Dietary Supplements / Q000706:statistics & numerical data; D005260:Female; D015577:Geriatric Assessment / Q000379:methods; D006801:Humans; D009043:Motor Activity / Q000502:physiology; D053580:Muscle Strength / Q000502:physiology; D010281:Parathyroid Hormone / Q000097:blood; D011597:Psychomotor Performance; D014481:United States / Q000453:epidemiology; D014807:Vitamin D / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000097:blood
chemical_list: C470125:PTH protein, human; D010281:Parathyroid Hormone; D014807:Vitamin D; C104450:25-hydroxyvitamin D; D002117:Calcitriol