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.
Conclusion: 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.