title: Obesity interacts with infectious mononucleosis in risk of multiple sclerosis.
abstract: OBJECTIVE
  The possible interaction between adolescent obesity and past infectious mononucleosis (IM) was investigated with regard to multiple sclerosis (MS) risk.
  
  
  METHODS
  This report is based on two population-based case-control studies, one with incident cases (1780 cases, 3885 controls) and one with prevalent cases (4502 cases, 4039 controls). Subjects were categorized based on adolescent body mass index (BMI) and past IM and compared with regard to occurrence of MS by calculating odds ratios with 95% confidence intervals (CIs) employing logistic regression. A potential interaction between adolescent BMI and past IM was evaluated by calculating the attributable proportion due to interaction.
  
  
  RESULTS
  Regardless of human leukocyte antigen (HLA) status, a substantial interaction was observed between adolescent obesity and past IM with regard to MS risk. The interaction was most evident when IM after the age of 10 was considered (attributable proportion due to interaction 0.8, 95% CI 0.6-1.0 in the incident study, and attributable proportion due to interaction 0.7, 95% CI 0.5-1.0 in the prevalent study). In the incident study, the odds ratio of MS was 14.7 (95% CI 5.9-36.6) amongst subjects with adolescent obesity and past IM after the age of 10, compared with subjects with none of these exposures. The corresponding odds ratio in the prevalent study was 13.2 (95% CI 5.2-33.6).
  
  
  CONCLUSIONS
  An obese state both impacts the cellular immune response to infections and induces a state of chronic immune-mediated inflammation which may contribute to explain our finding of an interaction between adolescent BMI and past IM. Measures taken against adolescent obesity may thus be a preventive strategy against MS.
authors.affiliation: Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: A K
authors.initials: AK
authors.lastname: Hedström
authors.forename: I
authors.initials: I
authors.lastname: Lima Bomfim
authors.forename: J
authors.initials: J
authors.lastname: Hillert
authors.forename: T
authors.initials: T
authors.lastname: Olsson
authors.forename: L
authors.initials: L
authors.lastname: Alfredsson
mesh_terms: D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D002648:Child; D005260:Female; D006801:Humans; D007244:Infectious Mononucleosis / Q000453:epidemiology*; D007249:Inflammation / Q000150:complications / Q000453:epidemiology* / Q000209:etiology; D008297:Male; D009103:Multiple Sclerosis / Q000453:epidemiology* / Q000209:etiology; D063766:Pediatric Obesity / Q000150:complications / Q000453:epidemiology*; D012306:Risk; D055815:Young Adult
keywords: Epstein−Barr virus; case-control study; demyelinating diseases; epidemiology; infectious mononucleosis; multiple sclerosis; obesity; risk factors