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Copyright ©The Author(s) 2016. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Jan 21, 2016; 22(3): 1088-1100
Published online Jan 21, 2016. doi: 10.3748/wjg.v22.i3.1088
Influence of environmental factors on the onset and course of inflammatory bowel disease
Amit Kumar Dutta, Ashok Chacko
Amit Kumar Dutta, Department of Gastrointestinal Sciences, Christian Medical College, Vellore 632004, India
Amit Kumar Dutta, Department of Digestive Disorders, Aberdeen Royal Infirmary, Aberdeen AB24 3FX, United Kingdom
Ashok Chacko, Institute of Gastroenterology and Liver Disease, The Madras Medical Mission, Chennai 600037, India
Author contributions: Dutta AK was involved in the search and review of the literature and preparation of the manuscript; Chacko A was involved in the concept of this study, search and review of the literature, preparation of the manuscript and critical appraisal.
Conflict-of-interest statement: The authors declare that they have no conflict of interest.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See:
Correspondence to: Ashok Chacko, Professor, Director, Institute of Gastroenterology and Liver Disease, The Madras Medical Mission, Chennai 600037, India.
Telephone: +91-44-26565961 Fax: +91-44-26565906
Received: April 26, 2015
Peer-review started: April 27, 2015
First decision: August 31, 2015
Revised: September 24, 2015
Accepted: November 30, 2015
Article in press: November 30, 2015
Published online: January 21, 2016

Numerous environmental factors have been linked with inflammatory bowel disease. These include smoking, diet, hygiene, drugs, geographical and psychosocial factors. These factors may either increase the risk of or protect against developing this condition and can also affect the course of illness in a positive or negative manner. A number of studies have examined the influence of environmental factors on inflammatory bowel diseases as a whole as well as on ulcerative colitis and Crohn’s disease separately. As there are differences in the pathogenesis of ulcerative colitis and Crohn’s disease, the effect of environmental factors on their onset and course is not always similar. Some factors have shown a consistent association, while reports on others have been conflicting. In this article we discuss the current evidence on the roles of these factors on inflammatory bowel disease, both as causative/protective agents and as modifiers of disease course.

Keywords: Environmental factors, Crohn’s disease, Ulcerative colitis, Etiology, Outcome

Core tip: Environmental factors have an important influence on the onset and course of inflammatory bowel disease. Multiple factors have been implicated with some showing a consistent effect, while the roles of others have been variable. The current evidence on their role in inflammatory bowel disease is discussed. A better understanding of these factors may help plan future preventive strategies.