Smoking is associated with risk for developing inflammatory bowel disease including late onset ulcerative colitis: a prospective study.

Objectives: Life style factors have been associated with inflammatory bowel disease (IBD) but there is a lack of data on the exposure of life styles factors before the onset of IBD. Our aim was to study the association between lifestyle factors and the development of IBD in a prospective setting.Materials and methods: We performed a case control study of 72 patients who later developed ulcerative colitis (UC), 26 patients who developed Crohn's disease (CD) and 427 healthy controls from the Vasterbotten intervention project matched for gender, age, year of health survey and area of residence. At recruitment, participants completed validated lifestyle questionnaires including data on alcohol intake. Information from this was used to assess the connection between lifestyle factors and later developing IBD.Results: For CD and UC, the median age at diagnosis was 53 and 52 years and median time of survey was 4 and 6 years before diagnosis, respectively. Multivariate odds ratio (OR) showed an association between never smoking and not developing IBD, including both UC and CD, OR (95% CI) 0.341 (0.136-0.853) and 0.473 (0.259-0.864), respectively. Marital status, educational level, alcohol consumption, reported physical activity and use of moist smokeless tobacco (snus) did not differ between patients and controls.Conclusions: Smoking proves to be a risk factor for both CD and UC in this prospective case-control study. No association was seen for snus users, implying a non-nicotine pathogenic mechanism from combusted tobacco.