title: Serum 25-hydroxyvitamin D and physical performance in postmenopausal women.
abstract: BACKGROUND
  Impairments in physical performance increase sharply with age. Low serum 25-hydroxyvitamin D (25-OHD) levels may be a modifiable risk factor for physical performance decline.
  
  
  METHODS
  Five hundred thirty-two participants in the Women's Health Initiative Clinical Trial (WHI CT) were among a 25% randomly selected subsample of women who participated in performance-based measures of physical performance at baseline, year 1, year 3, and year 6. A physical performance summary score was derived from three tests: timed walk, chair-stand, and grip strength. Levels of 25-OHD were measured at baseline. We used the generalized estimating equations (GEE) method to examine repeated measures of physical performance as a function of follow-up time since baseline according to 25-OHD concentration.
  
  
  RESULTS
  In 6 years of follow-up, participants with serum 25OHD ≥75 nmol/L had significantly higher scores for physical performance (β=2.64, 95% confidence interval [CI] 0.90-4.39) compared with the reference category (<35 nmol/L) after adjustment for age, chronic conditions, body mass index (BMI), race/ethnicity, time spent walking outside, trial arm, clinic latitude, and season of blood draw. However, the rate of decline in physical performance did not differ by level of 25OHD.
  
  
  CONCLUSIONS
  Higher baseline serum 25-OHD was associated with better physical performance but did not reduce decline in physical performance over the 6-year period.
authors.affiliation: Department of Epidemiology and Biostatistics, Drexel University, 1505 Race Street, Philadelphia, PA 19102, USA. michaely@drexel.edu
authors.forename: Yvonne L
authors.initials: YL
authors.lastname: Michael
authors.forename: Ellen
authors.initials: E
authors.lastname: Smit
authors.forename: Rebecca
authors.initials: R
authors.lastname: Seguin
authors.forename: J David
authors.initials: JD
authors.lastname: Curb
authors.forename: Lawrence S
authors.initials: LS
authors.lastname: Phillips
authors.forename: JoAnn E
authors.initials: JE
authors.lastname: Manson
mesh_terms: D000368:Aged; D002986:Clinical Trials as Topic; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D017698:Postmenopause / Q000502:physiology*; D012044:Regression Analysis; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D016387:Women's Health
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D