Daniel P Jones1,2, Tom G Richardson1,3, George Davey Smith1,3,4, David Gunnell1,4, Marcus R Munafò3,4,5,6, Robyn E Wootton3,4,6. 1. Department of Population Health Sciences, Bristol Medical School, University of Bristol, Bristol, UK. 2. Southmead Hospital, Westbury-on-Trym, Bristol, UK. 3. MRC Integrative Epidemiology Unit, Bristol, UK. 4. NIHR Biomedical Research Centre, University Hospitals Bristol NHS Foundation Trust, University of Bristol, Bristol, UK. 5. UK Centre for Tobacco and Alcohol Studies, University of Bristol, Bristol, UK. 6. School of Psychological Science, University of Bristol, Bristol, UK.
Abstract
BACKGROUND: Previous observational evidence has suggested an association between smoking and inflammatory bowel disease (IBD). METHODS: We used observational techniques followed by Mendelian randomization to explore whether smoking is a causal factor in the development of IBD and its subtypes. RESULTS: In those who have ever smoked, we observed increased risk of IBD and, in current smokers, we observed increased risk of Crohn disease and decreased risk of ulcerative colitis. However, our Mendelian randomization analyses found little evidence that smoking affects the development of IBD. CONCLUSION: Overall, our results suggest that smoking does not causally influence the risk of IBD.
BACKGROUND: Previous observational evidence has suggested an association between smoking and inflammatory bowel disease (IBD). METHODS: We used observational techniques followed by Mendelian randomization to explore whether smoking is a causal factor in the development of IBD and its subtypes. RESULTS: In those who have ever smoked, we observed increased risk of IBD and, in current smokers, we observed increased risk of Crohn disease and decreased risk of ulcerative colitis. However, our Mendelian randomization analyses found little evidence that smoking affects the development of IBD. CONCLUSION: Overall, our results suggest that smoking does not causally influence the risk of IBD.
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