title: The role of domestic hygiene in inflammatory bowel diseases: hepatitis A and worm infestations.
abstract: BACKGROUND
  Environmental factors are likely to be involved in the pathogenesis of inflammatory bowel disease (IBD), as the incidence of both Crohn's disease (CD) and ulcerative colitis (UC) increased with improved living standards in Europe after World War II. On the basis of earlier reports suggesting that hygienic standards may also play a role in the pathogenesis of IBD, we investigated the influence of hepatitis A seroprevalence as an indicator for poorer hygienic conditions and worm infestations in IBD.
  
  
  METHODS
  Hepatitis A seroprevalence was examined in patients with UC and CD. Patients with minor endocrinological disorders served as controls. All patients were questioned about immunizations, parasitic infections (worms), contact with animals, living on a farm, and ever traveling abroad. Patients were excluded for active hepatitis A immunization or recent passive immunization. Results are presented as Mantel-Haenszel odds ratios with 95% confidence interval, adjusted for age group.
  
  
  RESULTS
  The sample included 307 patients (73 CD, 48 UC, and 186 controls). Hepatitis A seroprevalence was strongly associated with age older than 50 years. Age adjusted Mantel-Haenszel odds ratios were 0.25 (0.09-0.71) for UC and 0.75 (0.38-1.46) for CD versus controls. For parasitic infections, the odds ratios were 1.15 (0.52-2.53) for UC and 0.34 (0.13-0.89) for CD.
  
  
  CONCLUSIONS
  We were able to demonstrate a negative association of hepatitis A infection with UC only. In contrast, a novel finding was a strong protective effect of worm infestations for the occurrence of CD, but not UC.
authors.affiliation: Department of Internal Medicine I, University of Regensburg, Regensburg, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Hafner
authors.forename: Antje
authors.initials: A
authors.lastname: Timmer
authors.forename: Hans
authors.initials: H
authors.lastname: Herfarth
authors.forename: Gerhard
authors.initials: G
authors.lastname: Rogler
authors.forename: Jürgen
authors.initials: J
authors.lastname: Schölmerich
authors.forename: Andreas
authors.initials: A
authors.lastname: Schäffler
authors.forename: Boris
authors.initials: B
authors.lastname: Ehrenstein
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Jilg
authors.forename: Claudia
authors.initials: C
authors.lastname: Ott
authors.forename: Ulrike G
authors.initials: UG
authors.lastname: Strauch
authors.forename: Florian
authors.initials: F
authors.lastname: Obermeier
mesh_terms: D000328:Adult; D017677:Age Distribution; D000367:Age Factors; D003093:Colitis, Ulcerative / Q000453:epidemiology / Q000209:etiology; D003424:Crohn Disease / Q000453:epidemiology / Q000209:etiology; D004812:Epidemiologic Methods; D005260:Female; D005858:Germany / Q000453:epidemiology; D006373:Helminthiasis / Q000453:epidemiology*; D006506:Hepatitis A / Q000453:epidemiology*; D006801:Humans; D006920:Hygiene; D015212:Inflammatory Bowel Diseases / Q000453:epidemiology* / Q000209:etiology; D008297:Male; D008875:Middle Aged