title: Cigarette smoking and the risk of multiple sclerosis: a sibling case-control study in Isfahan, Iran.
abstract: OBJECTIVE
  We aimed to study the smoking habits of multiple sclerosis (MS) patients and their healthy siblings in Isfahan province in Iran.
  
  
  METHODS
  MS patients registered with the Isfahan MS society database were compared to their healthy siblings who served as controls. Data regarding the smoking habits of patients and their siblings were collected using a specially designed questionnaire. Conditional logistic regression was adopted to analyze the association of smoking with the risk of MS, adjusting for age and sex.
  
  
  RESULTS
  There were 1,606 participants with 516 cases and 1,090 controls. After adjustments for age and sex, subjects who were ever-smokers had a significant risk of developing MS [odds ratio (OR) 2.67; 95% confidence interval (CI) 1.70-4.21; p <0.001]. Past smokers (OR 8.83; 95% CI 3.98-19.60; p < 0.001) and current smokers (OR 1.84; 95% CI 1.10-3.10; p = 0.021) had a significant risk for developing MS. Disease progression (current expanded disability status scale/disease duration) was not different between smokers and nonsmokers (0.54 ± 0.42 vs. 0.49 ± 0.48; p = 0.61).
  
  
  CONCLUSIONS
  Using a sibling pair method our data confirm the association between smoking and MS. A degree of confounding due to overmatching between siblings was unavoidable, but any bias would be conservative and should have lessened the effect of smoking.
authors.affiliation: Isfahan Neurosciences Research Centre, Isfahan University of Medical Sciences, Isfahan, Iran. Maghzi@edc.mui.ac.ir
authors.forename: Amir-Hadi
authors.initials: AH
authors.lastname: Maghzi
authors.forename: Masoud
authors.initials: M
authors.lastname: Etemadifar
authors.forename: Kiyan
authors.initials: K
authors.lastname: Heshmat-Ghahdarijani
authors.forename: Vahab
authors.initials: V
authors.lastname: Moradi
authors.forename: Safieh
authors.initials: S
authors.lastname: Nonahal
authors.forename: Abbas
authors.initials: A
authors.lastname: Ghorbani
authors.forename: Alireza
authors.initials: A
authors.lastname: Minagar
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D018450:Disease Progression; D005260:Female; D006801:Humans; D007492:Iran / Q000453:epidemiology; D008297:Male; D020528:Multiple Sclerosis, Chronic Progressive / Q000453:epidemiology*; D020529:Multiple Sclerosis, Relapsing-Remitting / Q000453:epidemiology*; D012307:Risk Factors; D035781:Siblings; D012907:Smoking / Q000009:adverse effects / Q000453:epidemiology*