Military history of patients with inflammatory bowel disease:: An epidemiological study among US veterans

Objectives: The military history of patients with inflammatory bowel disease (IBD) contains types of exposure that are not available through other sources and may provide clues about the as-yet unknown etiology of IBD. We therefore sought to describe the epidemiology of IBD among veterans, with particular emphasis on their military history. Methods: A case-control study compared 10,544 IBD patients and 42,026 controls with respect to age, gender, ethnicity, time period of military service, military duty in Vietnam, status as prisoner of war, and exposure to Agent Orange. Results: Subjects with Crohn's disease were younger than those with ulcerative colitis or without IBD (odds ratio: 0.85; 95% confidence interval [CI]: 0.83-0.87). Both types of IBD affected female veterans significantly more often than male veterans, the relative female predominance being more pronounced in Crohn's disease than ulcerative colitis (0.70; 0.61-0.81 vs 0.83; 0.71-0.96). Whites were more prone to develop both types of IBD than nonwhites (2.46; 2.27-2.68 vs 2.11; 1.95-2.27). Military duty in Vietnam and a status as prisoner of war both exerted a protective influence against Crohn's disease (0.84; 0.75-0.96 and 0.60; 0.41-0.87, respectively), but not ulcerative colitis. Conclusions: The results are consistent with the hypothesis that exposure to poor sanitation decreases the future risk of developing Crohn's disease. (Am J Gastroenterol 1998;93:1457-1462. (C) 1998 by Am. Cell. of Gastroenterology).