title: Asthma and multiple sclerosis: an inverse association in a case-control general practice population.
abstract: BACKGROUND
  Th1/Th2 imbalance is hypothesized to up-regulate some diseases and down-regulate others. Compared to controls, multiple sclerosis (MS) (Th1-mediated) has been linked to a reduced risk of allergy and asthma (Th2-mediated), based on patient questionnaire studies and a review of asthma medication.
  
  
  OBJECTIVE
  To investigate whether MS is associated with a reduced risk of Th2-associated diseases and an increased risk of Th1-associated diseases.
  
  
  METHODS
  Retrospective matched case-control study.
  
  
  METHODS
  Three hundred and twenty MS patients and controls matched for age, gender, location and smoking were selected from the Welsh General Practice Morbidity Database from 1995-99. Case and control records were assessed for Th1-mediated and Th2-mediated diseases.
  
  
  RESULTS
  Overall, 346 MS patients were identified, giving a prevalence of 127 per 100 000. There was an inverse relationship between multiple sclerosis (MS) and asthma (OR 0.33; 95%CI 0.15-0.77). No statistically significant relationships emerged between other Th2-associated (eczema, dermatitis) or any Th1-associated (rheumatoid arthritis, thyroid disorders, inflammatory bowel disease [IBD], type 1 diabetes) diseases and MS, although no patient in either group had treated type 1 diabetes. A trend existed for IBD, with 5/320 of cases affected and no controls; OR infinity; 95%CI 1.30-infinity; p=0.063.
  
  
  CONCLUSIONS
  This inverse association between MS and asthma is compatible with a Th1/Th2 imbalance. Although the Th1/Th2 theory is probably an over-simplification in MS, a shift from Th1 cytokine dominance towards Th2 may provide drug-targeting routes for MS.
authors.affiliation: Department of Medicine (Neurology), University of Wales College of Medicine, Cardiff, Wales, UK. tremlett@interchange.ubc.ca
authors.forename: H L
authors.initials: HL
authors.lastname: Tremlett
authors.forename: J
authors.initials: J
authors.lastname: Evans
authors.forename: C M
authors.initials: CM
authors.lastname: Wiles
authors.forename: D K
authors.initials: DK
authors.lastname: Luscombe
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001172:Arthritis, Rheumatoid / Q000453:epidemiology; D001249:Asthma / Q000150:complications / Q000453:epidemiology* / Q000276:immunology; D016022:Case-Control Studies; D003922:Diabetes Mellitus, Type 1 / Q000453:epidemiology; D004485:Eczema / Q000453:epidemiology; D005194:Family Practice; D005260:Female; D006801:Humans; D015212:Inflammatory Bowel Diseases / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000150:complications / Q000453:epidemiology* / Q000276:immunology; D012189:Retrospective Studies; D012307:Risk Factors; D014852:Wales / Q000453:epidemiology