The main goals of this study are (1) to determine whether current and past use of oral contraceptives alter a woman's risk of developing ulcerative colitis (2) to determine whether alteration in risk due to oral contraceptive use varies according to durations of use, timing of use, or the estrogen/progestin content of the preparation(s) used; and (3) to determine whether any change in risk due to oral contraceptive use is confounded or modified by other exposures, illnessess, or personal characteristics. To accomplish these aims a population based case-control study will be conducted among members of a pre-paid health plan serving residents of Washington State (Group Health Cooperative). Cases will be identified by review of medical records and computer files of hospital discharge summary diagnoses. Pharmacy computerized data will be reviewed for all persons who received a prescription for sulfasalazine, a medication primarily used for the treatment of ulcerative colitis. Ongoing surveillance for incident cases of ulcerative colitis will be performed by the Group Health Cooperative (GHC) gastroenterologists for a period of four years. Four female-age matched controls per case will be randomly selected from the GHC enrollment file. Subjects will be interviewed in person about current and past use of oral contraceptives and about other relevant exposures and characteristics, such as childbearing history, socioeconomic status, indication for use of oral contraceptives, and smoking history. A previously validated interview instrument for measurement of oral contraceptive use will be employed. Traditional methods for matched analysis and conditional logistic regression will be used to estimate the odds ratio for ulcerative colitis among oral contraceptive users while adjusting for potential confounding factors.
| Boyko, E J; Theis, M K; Vaughan, T L et al. (1994) Increased risk of inflammatory bowel disease associated with oral contraceptive use. Am J Epidemiol 140:268-78 |
