title: Risk factors for inflammatory bowel disease in the general population.
abstract: BACKGROUND
  The aetiology of inflammatory bowel disease remains largely unknown.
  
  
  OBJECTIVE
  We performed a comprehensive assessment of potential risk factors associated with the occurrence of inflammatory bowel disease.
  
  
  METHODS
  We identified a cohort of patients 20-84 years old between 1995 and 1997 registered in the General Practitioner Research Database in the UK. A total of 444 incident cases of IBD were ascertained and validated with the general practitioner. We performed a nested case-control analysis using all cases and a random sample of 10 000 frequency-matched controls.
  
  
  RESULTS
  Incidence rates for ulcerative colitis, Crohn's disease, and indeterminate colitis were 11, 8, and 2 cases per 100 000 person-years, respectively. Among women, we found that long-term users of oral contraceptives were at increased risk of developing UC (OR: 2.35; 95% CI: 0.89-6.22) and CD (OR: 3.15; 95% CI: 1.24-7.99). Similarly, long-term users of HRT had an increased risk of CD (OR: 2.60; 95% CI: 1.04-6.49) but not UC. Current smokers experienced a reduced risk of UC along with an increased risk of CD. Prior appendectomy was associated with a decreased the risk of UC (OR: 0.37; 95% CI: 0.14-1.00).
  
  
  CONCLUSIONS
  Our results support the hypothesis of an increased risk of inflammatory bowel disease associated with oral contraceptives use and suggest a similar effect of hormone replacement therapy on CD. We also confirmed the effects of smoking and appendectomy on inflammatory bowel disease.
authors.affiliation: Centro Español de Investigación Farmacoepidemiológica (CEIFE), Madrid, Spain.
authors.forename: L A
authors.initials: LA
authors.lastname: García Rodríguez
authors.forename: A
authors.initials: A
authors.lastname: González-Pérez
authors.forename: S
authors.initials: S
authors.lastname: Johansson
authors.forename: M-A
authors.initials: MA
authors.lastname: Wallander
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000009:adverse effects; D001062:Appendectomy / Q000009:adverse effects; D001241:Aspirin / Q000009:adverse effects; D003276:Contraceptives, Oral / Q000009:adverse effects; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D015212:Inflammatory Bowel Diseases / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D012907:Smoking / Q000009:adverse effects / Q000453:epidemiology; D013548:Sweden / Q000453:epidemiology
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D003276:Contraceptives, Oral; D001241:Aspirin