title: Higher 25-hydroxyvitamin D is associated with lower relapse risk in multiple sclerosis.
abstract: OBJECTIVE
  A protective association between higher vitamin D levels and the onset of multiple sclerosis (MS) has been demonstrated; however, its role in modulating MS clinical course has been little studied. We investigated whether higher levels of serum 25-hydroxyvitamin D (25-OH-D) were associated with a lower risk of relapses in people with MS.
  
  
  METHODS
  We conducted a prospective cohort study of 145 participants with relapsing-remitting MS from 2002 to 2005. Serum 25-OH-D levels were measured biannually, and the hazard of relapse was assessed using survival analysis.
  
  
  RESULTS
  There was an inverse linear relationship between 25-OH-D levels and the hazard of relapse over the subsequent 6 months, with hazard ratio (HR) 0.91 (95% confidence interval [CI]: 0.85-0.97) per 10 nmol/l increase in 25-OH-D level (p = 0.006). When variation due to timing of blood collection was removed by estimating 25-OH-D at the start of each season, this association persisted, with HR 0.90 (95% CI, 0.83-0.98) per 10 nmol/l increase (p = 0.016). Taking into account the biological half-life of 25-OH-D, we estimated 25-OH-D at monthly intervals, resulting in a slightly enhanced association, with HR 0.88 (95% CI, 0.82-0.95) per 10 nmol/l increase (p = 0.001). Adjusting for potential confounders did not alter these findings.
  
  
  CONCLUSIONS
  In this prospective population-based cohort study, in a cohort largely on immunomodulatory therapy, higher 25-OH-D levels were associated with a reduced hazard of relapse. This occurred in a dose-dependent linear fashion, with each 10 nmol/l increase in 25-OH-D resulting in up to a 12% reduction in risk of relapse. Clinically, raising 25-OH-D levels by 50 nmol/l could halve the hazard of a relapse.
authors.affiliation: Menzies Research Institute, Hobart TAS, Australia.
authors.forename: Steve
authors.initials: S
authors.lastname: Simpson
authors.forename: Bruce
authors.initials: B
authors.lastname: Taylor
authors.forename: Leigh
authors.initials: L
authors.lastname: Blizzard
authors.forename: Anne-Louise
authors.initials: AL
authors.lastname: Ponsonby
authors.forename: Fotini
authors.initials: F
authors.lastname: Pittas
authors.forename: Helen
authors.initials: H
authors.lastname: Tremlett
authors.forename: Terence
authors.initials: T
authors.lastname: Dwyer
authors.forename: Peter
authors.initials: P
authors.lastname: Gies
authors.forename: Ingrid
authors.initials: I
authors.lastname: van der Mei
mesh_terms: D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000032:analysis / Q000097:blood; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D020529:Multiple Sclerosis, Relapsing-Remitting / Q000097:blood* / Q000175:diagnosis / Q000453:epidemiology*; D011446:Prospective Studies; D012008:Recurrence; D018570:Risk Assessment; D012307:Risk Factors; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D055815:Young Adult
chemical_list: D015415:Biomarkers; D014807:Vitamin D; C104450:25-hydroxyvitamin D