INCREASED RISK OF INFLAMMATORY BOWEL-DISEASE ASSOCIATED WITH ORAL-CONTRACEPTIVE USE

Research on inflammatory bowel disease risk among oral contraceptive u sers has reached conflicting conclusions. This population-based case-c ontrol study evaluated the effects of oral contraceptive use on ulcera tive colitis and Crohn's disease risk. Cases were women enrollees, age d 15-68 years, of Group Health Cooperative of Puget Sound (a prepaid h ealth plan based in western Washington State) who had ulcerative colit is (n = 211) or Crohn's disease (n = 91). Age-matched controls were ra ndomly selected from the health plan enrollment file. An in-person int erview obtained information about lifetime contraceptive use. Conditio nal logistic regression analysis was used to estimate relative risks a nd 95% confidence intervals for disease. Women who reported oral contr aceptive use within 6 months before disease onset were at increased ri sk for both diseases compared with never users (relative risk (RR) of ulcerative colitis = 2.0, 95% confidence interval (Cl) 1.2-3.3; RR of Crohn's disease = 2.6, 95% CI 1.2-5.5). Women who had used oral contra ceptives for more than 6 years had the highest risk of Crohn's disease (RR = 5.1, 95% CI 1.8-14.3). In contrast, increasing duration of use was not associated with increased risk of ulcerative colitis. Adjustme nt for race, smoking, income, or pregnancy history did not substantial ly alter these results. Higher ulcerative colitis risk tended to occur among users of high estrogen dose oral contraceptives, while Crohn's disease risk was similar regardless of estrogen potency.