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Background: Environmental exposures in early life have been implicated in the aetiology of inflammatory bowel disease. Objective: To examine environmental risk factors prior to the development of inflammatory bowel disease in a paediatric population based case control study. Methods: A total of 222 incident cases of Crohn’s disease and 60 incident cases of ulcerative colitis occurring before 17 years of age between January 1988 and December 1997 were matched with one control subject by sex, age, and geographical location. We recorded 140 study variables in a questionnaire that covered familial history of inflammatory bowel disease, events during the perinatal period, infant and child diet, vaccinations and childhood diseases, household amenities, and the family’s socioeconomic status. Results: In a multivariate model, familial history of inflammatory bowel disease (odds ratio (OR) 4.3 (95% confidence interval 2.3–8)), breast feeding (OR 2.1 (1.3–3.4)), bacille Calmette-Guerin vaccination (OR 3.6 (1.1–11.9)), and history of eczema (OR 2.1 (1–4.5)) were significant risk factors for Crohn’s disease whereas regular drinking of tap water was a protective factor (OR 0.56 (0.3–1)). Familial history of inflammatory bowel disease (OR 12.5 (2.2–71.4)), disease during pregnancy (OR 8.9 (1.5–52)), and bedroom sharing (OR 7.1 (1.9–27.4)) were risk factors for ulcerative colitis whereas appendicectomy was a protective factor (OR 0.06 (0.01–0.36)). Conclusions: While family history and appendicectomy are known risk factors, changes in risk based on domestic promiscuity, certain vaccinations, and dietary factors may provide new aetiological clues.

BACKGROUNDSubjects without known colorectal adenomas or cancer constitute a large majority of the population where 85% of all cases of colorectal cancer are thought to occur. Consequently these people should be considered for screening to decrease mortality from colorectal cancer in the general population.AIMSTo estimate the incidence rate of rectosigmoid adenomas in these subjects.METHODSSubjects without adenomas or cancer at a previous examination which had visualised the rectosigmoid underwent a fibre endoscopy every three years. Endoscopic data and population characteristics were collected prospectively.RESULTSA total of 450 subjects fulfilled the selection criteria; 287 (64%) underwent at least two examinations, and 163 had three or more. At the second examination, with a mean delay of 39 months, the incidence rate of rectosigmoïd adenomas was 1.50% per patient year. The rate was 1.75% per patient year (95% CI 0.80–3.33) at the third endoscopy with an additional mean delay of 38 months. The cumulative incidence rate at six years was 7.3% (95% CI 4.3–10.3), representing a mean of 1.2% per patient year. This rate increased with age and was higher for men than for women after age adjustment (p< 0.03).CONCLUSIONSThe incidence rates are very low compared with those of patients with prior adenomas. These results should be considered in establishing rectosigmoid adenoma screening strategies.