Question What are the risk factors for Crohn's disease in remission? Design 48 week study of patients in the placebo group of a randomised controlled trial. Setting 31 clinical centres in Canada. Patients 152 patients (median age 34 y, 58% women) who were 18-82 years of age; had Crohn's disease with greater than or equal to 2 exacerbations in the previous 4 years and 1 exacerbation or surgical resection in the previous 18 months; were in remission (Crohn's Disease Activity Index less than or equal to 150); and had not received treatment with corticosteroids for greater than or equal to 30 days, immunosuppressants for less than or equal to 90 days, and mesalazine or metronidazole for 7 days before study entry. Exclusion criteria were a history of proctocolectomy or malignant disease, short bowel syndrome, >3 bowel resections in the previous 10 years, chronic perianal disease, drug abuse, or major illness. Assessment of risk factors Smoking, use of oral contraceptives, disease location and duration, age at diagnosis, time in remission, recent resection, history of blood transfusions, baseline disease activity, and quality of life were assessed in personal interviews. Main outcome measure Relapse. Main results 61 patients relapsed, 60 patients remained in remission, and 31 patients were withdrawn without relapse. Relapses occurred more frequently in women than in men (46% v 33%, p = 0.05) and in patients who achieved remission after medical treatment than after surgery (46% v 25%, p = 0.02). Relapse was also associated with smoking status (current smokers 53%, former smokers 35%, non-smokers 30%; p = 0.02) and oral contraceptive use (current use 43%, previous use 70%, no use 27%; p < 0.001). Multivariate analysis showed that an increased risk of relapse was associated with current smoking, previous or current oral contraceptive use, and medical induction of remission; sex and previous smoking were not associated with an increased risk of relapse (table). No interaction between smoking and oral contraceptive use occurred. Conclusion Current smoking, previous or current oral contraceptive use, and medical induction of remission were independent risk factors for relapse in patients with Crohn's disease in remission.
