title: Seasonal periodicity of serum vitamin D and parathyroid hormone, bone resorption, and fractures: the Geelong Osteoporosis Study.
abstract: In this population-based study, seasonal periodicity was seen with reduced serum vitamin D, increased serum PTH, and increased bone resorption in winter. This was associated with an increased proportion of falls resulting in fracture and an increased risk of wrist and hip fractures.
  
  
  BACKGROUND
  In a population of women who reside in a temperate climate and do not generally receive dietary vitamin D supplementation, we investigated whether seasonal vitamin D insufficiency is associated with increased risk of fracture.
  
  
  METHODS
  An observational, cross-sectional, population-based study set in southeastern Australia (latitude 38-39 degrees S). Participants were drawn from a well-defined community of 27,203 women >/=55 years old: 287 randomly selected from electoral rolls, 1635 with incident fractures, and 1358 presenting to a university hospital with falls. The main outcome measures were annual periodicities of ultraviolet radiation, serum 25-hydroxyvitamin D [25(OH)D], serum parathyroid hormone (PTH), serum C-telopeptide (CTx), BMD, falls, and fractures.
  
  
  RESULTS
  Cyclic variations in serum 25(OH)D lagged 1 month behind ultraviolet radiation, peaking in summer and dipping in winter (p < 0.001). Periodicity of serum PTH was the inverse of serum 25(OH)D, with a phase shift delay of 1 month (p = 0.004). Peak serum CTx lagged peak serum PTH by 1-2 months. In late winter, a greater proportion of falls resulted in fracture (p < 0.001). Seasonal periodicity in 439 hip and 307 wrist fractures also followed a simple harmonic model (p = 0.078 and 0.002, respectively), peaking 1.5-3 months after the trough in 25(OH)D.
  
  
  CONCLUSIONS
  A fall in 25(OH)D in winter is accompanied by increases in (1) PTH levels, (2) bone resorption, (3) the proportion of falls resulting in fracture, and (4) the frequency of hip and wrist fracture. Whether vitamin D supplementation in winter can reduce the population burden of fractures requires further investigation.
authors.affiliation: Department of Clinical and Biomedical Sciences: Barwon Health, The University of Melbourne, Geelong, Victoria, Australia.
authors.forename: Julie A
authors.initials: JA
authors.lastname: Pasco
authors.forename: Margaret J
authors.initials: MJ
authors.lastname: Henry
authors.forename: Mark A
authors.initials: MA
authors.lastname: Kotowicz
authors.forename: Kerrie M
authors.initials: KM
authors.lastname: Sanders
authors.forename: Ego
authors.initials: E
authors.lastname: Seeman
authors.forename: John R
authors.initials: JR
authors.lastname: Pasco
authors.forename: Hans G
authors.initials: HG
authors.lastname: Schneider
authors.forename: Geoffrey C
authors.initials: GC
authors.lastname: Nicholson
mesh_terms: D000058:Accidental Falls / Q000706:statistics & numerical data; D000368:Aged; D000369:Aged, 80 and over; D015519:Bone Density / Q000502:physiology; D001862:Bone Resorption / Q000097:blood* / Q000453:epidemiology*; D003094:Collagen / Q000097:blood; D024042:Collagen Type I; D003430:Cross-Sectional Studies; D005260:Female; D050723:Fractures, Bone / Q000097:blood* / Q000453:epidemiology* / Q000209:etiology; D006620:Hip Fractures / Q000097:blood / Q000453:epidemiology / Q000209:etiology; D006801:Humans; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood*; D010455:Peptides / Q000097:blood; D010507:Periodicity; D012621:Seasons; D014466:Ultraviolet Rays; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood*; D014954:Wrist Injuries / Q000097:blood / Q000453:epidemiology / Q000209:etiology
chemical_list: D024042:Collagen Type I; D010281:Parathyroid Hormone; D010455:Peptides; C052929:collagen type I trimeric cross-linked peptide; D014807:Vitamin D; D003094:Collagen; C104450:25-hydroxyvitamin D