title: Sun exposure and vitamin D are independent risk factors for CNS demyelination.
abstract: OBJECTIVE
  To examine whether past and recent sun exposure and vitamin D status (serum 25-hydroxyvitamin D [25(OH)D] levels) are associated with risk of first demyelinating events (FDEs) and to evaluate the contribution of these factors to the latitudinal gradient in FDE incidence in Australia.
  
  
  METHODS
  This was a multicenter incident case-control study. Cases (n = 216) were aged 18-59 years with a FDE and resident within one of 4 Australian centers (from latitudes 27°S to 43°S), from November 1, 2003, to December 31, 2006. Controls (n = 395) were matched to cases on age, sex, and study region, without CNS demyelination. Exposures measured included self-reported sun exposure by life stage, objective measures of skin phenotype and actinic damage, and vitamin D status.
  
  
  RESULTS
  Higher levels of past, recent, and accumulated leisure-time sun exposure were each associated with reduced risk of FDE, e.g., accumulated leisure-time sun exposure (age 6 years to current), adjusted odds ratio (AOR) = 0.70 (95% confidence interval [CI] 0.53-0.94) for each ultraviolet (UV) dose increment of 1,000 kJ/m(2) (range 508-6,397 kJ/m(2)). Higher actinic skin damage (AOR = 0.39 [95% CI 0.17-0.92], highest grade vs the lowest) and higher serum vitamin D status (AOR = 0.93 [95% CI 0.86-1.00] per 10 nmol/L increase in 25(OH)D) were independently associated with decreased FDE risk. Differences in leisure-time sun exposure, serum 25(OH)D level, and skin type additively accounted for a 32.4% increase in FDE incidence from the low to high latitude regions.
  
  
  CONCLUSIONS
  Sun exposure and vitamin D status may have independent roles in the risk of CNS demyelination. Both will need to be evaluated in clinical trials for multiple sclerosis prevention.
authors.affiliation: National Centre for Epidemiology and Population Health, The Australian National University, Canberra 0200, Australia. Robyn.Lucas@anu.edu.au
authors.forename: R M
authors.initials: RM
authors.lastname: Lucas
authors.forename: A-L
authors.initials: AL
authors.lastname: Ponsonby
authors.forename: K
authors.initials: K
authors.lastname: Dear
authors.forename: P C
authors.initials: PC
authors.lastname: Valery
authors.forename: M P
authors.initials: MP
authors.lastname: Pender
authors.forename: B V
authors.initials: BV
authors.lastname: Taylor
authors.forename: T J
authors.initials: TJ
authors.lastname: Kilpatrick
authors.forename: T
authors.initials: T
authors.lastname: Dwyer
authors.forename: A
authors.initials: A
authors.lastname: Coulthard
authors.forename: C
authors.initials: C
authors.lastname: Chapman
authors.forename: I
authors.initials: I
authors.lastname: van der Mei
authors.forename: D
authors.initials: D
authors.lastname: Williams
authors.forename: A J
authors.initials: AJ
authors.lastname: McMichael
mesh_terms: D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D003711:Demyelinating Diseases / Q000097:blood* / Q000453:epidemiology* / Q000209:etiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000097:blood / Q000453:epidemiology / Q000209:etiology; D012307:Risk Factors; D013021:South Australia / Q000453:epidemiology; D013472:Sunlight; D013648:Tasmania / Q000453:epidemiology; D014739:Victoria / Q000453:epidemiology; D014807:Vitamin D / Q000008:administration & dosage / Q000097:blood*; D014808:Vitamin D Deficiency / Q000097:blood / Q000150:complications / Q000453:epidemiology; D055815:Young Adult
chemical_list: D014807:Vitamin D