title: Smoking and multiple sclerosis susceptibility.
abstract: Smoking is one of the most established risk factors for multiple sclerosis (MS). The aim of this study was to investigate how age at smoking debut, duration, intensity and cumulative dose of smoking, and smoking cessation influence the association between smoking and MS risk. In two Swedish population-based case-control studies (7,883 cases, 9,264 controls), subjects with different smoking habits were compared regarding MS risk, by calculating odds ratios with 95% confidence intervals. We observed a clear dose response association between cumulative dose of smoking and MS risk (p value for trend <10(-35)). Both duration and intensity of smoking contributed independently to the increased risk of MS. However, the detrimental effect of smoking abates a decade after smoking cessation regardless of the cumulative dose of smoking. Age at smoking debut did not affect the association between smoking and MS. Smoking increases the risk of MS in a dose response manner. However, in contrary to several other risk factors for MS that seem to affect the risk only if the exposure takes place during a specific period in life, smoking affects MS risk regardless of age at exposure, and the detrimental effect slowly abates after smoking cessation.
authors.affiliation: Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden, anna.hedstrom@ki.se.
authors.forename: Anna Karin
authors.initials: AK
authors.lastname: Hedström
authors.forename: Jan
authors.initials: J
authors.lastname: Hillert
authors.forename: Tomas
authors.initials: T
authors.lastname: Olsson
authors.forename: Lars
authors.initials: L
authors.lastname: Alfredsson
mesh_terms: D000328:Adult; D000367:Age Factors; D017668:Age of Onset; D016022:Case-Control Studies; D016001:Confidence Intervals; D004198:Disease Susceptibility; D005260:Female; D005838:Genotype; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000453:epidemiology / Q000209:etiology* / Q000235:genetics; D016017:Odds Ratio; D011159:Population Surveillance; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects*; D016540:Smoking Cessation / Q000706:statistics & numerical data; D012959:Socioeconomic Factors; D013548:Sweden / Q000453:epidemiology; D013997:Time Factors; D014029:Tobacco Use Disorder / Q000150:complications* / Q000453:epidemiology