title: Smoke exposure increases the risk for multiple sclerosis.
abstract: OBJECTIVE
  To estimate the effect of exposure to smoking on the risk for multiple sclerosis (MS), we analyzed nicotine metabolite (cotinine) levels in biobank samples from 109 MS cases and 218 matched referents.
  
  
  RESULTS
  Elevated cotinine levels, even modest elevations, were associated with an increased risk for MS (all other categories versus lowest: OR = 2.9; 95% CI: 1.3-6.3). A similar but non-significant risk increase was observed also in the small subset of individuals with samples collected before the onset of MS (all other categories versus lowest: OR = 2.4; 95% CI: 0.26-21). Elevated cotinine was associated with an increased risk for MS predominantly in women (all other categories versus lowest category: OR = 3.9; 95% CI: 1.3-12), whereas the risk increase in men was smaller and non-significant.
  
  
  CONCLUSIONS
  Smoke exposure is associated with a higher risk for MS than previously estimated. There seems to be a threshold effect present in the lower range of cotinine in its relation to MS. Modestly elevated cotinine levels suggestive of passive smoking are associated with an increased risk for MS. Smoke exposure may explain the higher incidence of MS in women. These preliminary findings need to be confirmed in an expanded material of prospectively collected samples.
authors.affiliation: Department of Neurology, Umeå University Hospital, Umeå, Sweden. peter.sundstrom@neuro.umu.se
authors.forename: P
authors.initials: P
authors.lastname: Sundström
authors.forename: L
authors.initials: L
authors.lastname: Nyström
authors.forename: G
authors.initials: G
authors.lastname: Hallmans
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D003367:Cotinine / Q000097:blood*; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000097:blood* / Q000453:epidemiology*; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects*
chemical_list: D003367:Cotinine