title: Factors affecting changes in the serum levels of 25-hydroxyvitamin D: a 3-year follow-up of the ROAD study.
abstract: In this 3-year population-based cohort study, among 1346 subjects, the mean annual change in the serum 25-hydroxyvitamin D levels was 7.6 %/year, which tended to increase during the 3-year period. Multivariate regression analysis indicated that the L2-4 bone mineral density and total daily energy intake were significant independent associated factors.
  
  
  BACKGROUND
  The aim of this study was to clarify the change rate of the serum levels of 25-hydroxyvitamin D (25D) and the associated factors in a general Japanese population during a 3-year period.
  
  
  METHODS
  The baseline survey of Research on Osteoarthritis/osteoporosis Against Disability study (ROAD), a large-scale population-based cohort study, was performed between 2005 and 2007, and a follow-up survey was repeated 3 years later. Among 1690 participants at baseline, the change rate of the serum 25D levels were assessed in 1346 individuals (79.6 %; 458 men and 888 women) who completed measurements of 25D at both the baseline and follow-up examinations. The change rate was calculated, and the factors associated with the changes in the 25D levels were determined using multivariate regression analysis after adjustment for age, gender, body mass index, participated month, and regional differences at baseline.
  
  
  RESULTS
  The mean (standard deviation) change rate of the 25D levels in all subjects was 7.6 (13.3) %/year (men, 8.2 [12.4] %/year; women, 7.3 [13.7] %/year). Multivariate regression analysis indicated that higher bone mineral density at lumbar spine L2-4 (p = 0.05) and total daily energy intake (p = 0.04) were significantly associated with the change rate of the 25D levels.
  
  
  CONCLUSIONS
  The serum levels of 25D tended to increase over the 3-year period, and higher lumbar bone mineral density and daily energy intake were found to be associated with increases in the 25D levels over time.
authors.affiliation: Department of Joint Disease Research, 22nd Century Medical and Research Center, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan. YOSHIMURAN-ORT@h.u-tokyo.ac.jp.
authors.forename: N
authors.initials: N
authors.lastname: Yoshimura
authors.affiliation: Department of Clinical Motor System Medicine, 22nd Century Medical and Research Center, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Muraki
authors.affiliation: Department of Medical Research and Management for Musculoskeletal Pain, 22nd Century Medical and Research Center, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Oka
authors.affiliation: Department of Orthopaedic Surgery, Faculty of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Tanaka
authors.affiliation: JCHO Tokyo Shinjuku Medical Center, 5-1, Tsukudo-cho, Shinjyuku-ku, Tokyo, 162-8542, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Kawaguchi
authors.affiliation: National Rehabilitation Center for Persons with Disabilities, 1, Namiki 4-chome, Tokorozawa City, Saitama Prefecture, 359-8555, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Nakamura
authors.affiliation: National Rehabilitation Center for Persons with Disabilities, 1, Namiki 4-chome, Tokorozawa City, Saitama Prefecture, 359-8555, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Akune
mesh_terms: D017677:Age Distribution; D000368:Aged; D000886:Anthropometry / Q000379:methods; D015519:Bone Density / Q000502:physiology; D002149:Energy Intake / Q000502:physiology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008159:Lumbar Vertebrae / Q000502:physiology; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D017678:Sex Distribution; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D
keywords: 25-Hydroxyvitamin D; Bone mineral density; Nutrition; Population-based cohort study; Risk factors