title: Low serum vitamin d does not predict new disability or loss of muscle strength in older women.
abstract: OBJECTIVE
  To determine whether serum levels of 25-hydroxyvitamin D (25(OH)D) and parathyroid hormone (PTH) predict accelerated decline in muscular strength or onset of new disability in mobility and upper extremity functioning over a 3-year follow-up.
  
  
  METHODS
  A community-based prospective cohort study.
  
  
  METHODS
  Six hundred twenty-eight moderately to severely disabled women aged 65 and older living in the community.
  
  
  METHODS
  Subjects were divided into three groups of baseline 25(OH)D serum levels (deficiency: <25 nmol/L; low normal: 25-52 nmol/L; high normal: > or =53 nmol/L) and into tertiles of PTH levels. Objective performance measures (hip flexor, knee extensor, and grip strengths; walking speed; and time for repeated chair stands) and disability in activities involving mobility and upper extremity function were assessed at baseline and every 6 months for 3 years. Decline in performance measures and onset of new disability were compared between 25(OH)D and PTH groups using random effects models and proportional hazards models, respectively, while adjusting for age, race, education, body mass index, baseline performance, and chronic conditions.
  
  
  RESULTS
  The annual rate of decline over 3 years in muscular strength, walking speed, and time to perform repeated chair stands was similar across 25(OH)D groups. We observed a nonsignificantly faster decline in proximal muscle strength and walking speed with increasing PTH levels. There was no association for either measure between serum levels and the risk of incident disability in activities relating to mobility and upper extremity function.
  
  
  CONCLUSIONS
  This study does not support the hypothesis that vitamin D deficiency is associated with loss in muscular strength and decline in mobility and upper extremity functioning over time in older women who were moderately to severely disabled at baseline.
authors.affiliation: Department of Social and Preventive Medicine, Faculty of Medicine, Laval University, Quebec City, Canada. rene.verreault@msp.ulaval.ca
authors.forename: René
authors.initials: R
authors.lastname: Verreault
authors.forename: Richard D
authors.initials: RD
authors.lastname: Semba
authors.forename: Stefano
authors.initials: S
authors.lastname: Volpato
authors.forename: Luigi
authors.initials: L
authors.lastname: Ferrucci
authors.forename: Linda P
authors.initials: LP
authors.lastname: Fried
authors.forename: Jack M
authors.initials: JM
authors.lastname: Guralnik
mesh_terms: D000367:Age Factors; D000368:Aged; D001132:Arm / Q000503:physiopathology*; D015331:Cohort Studies; D006233:Persons with Disabilities; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D009069:Movement Disorders / Q000097:blood* / Q000503:physiopathology*; D018482:Muscle, Skeletal / Q000503:physiopathology*; D010281:Parathyroid Hormone / Q000097:blood*; D010807:Physical Endurance / Q000502:physiology*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012737:Sex Factors; D013997:Time Factors; D014807:Vitamin D / Q000097:blood*
chemical_list: D010281:Parathyroid Hormone; D014807:Vitamin D