The role of environmental risk factors in the etiology of inflammatory bowel di̇seases: A multi̇center study

Inflammatory bowel disease (IBD) is a chronic inflammatory disease of the gastrointestinal tract, which has two subtypes; ulcerative colitis (UC) and Crohn's disease (CH), with distinct clinical and prognostic differences. The global increase in the incidence and prevalence of IBD in recent years has led to the discovery of important environmental factors that may be associated with the disease etiology. This multicenter case-control study, aims to examine the environmental risk factors that may cause the development of IBD in Turkey. The study was conducted with 3 groups including a total of 901 people consisting of 277 ulcerative colitis patients, 156 Crohn's patients and 468 healthy volunteers (matched one to one according to age and gender) who applied to the outpatient clinic between 01.11.2020 and 30.12.2021 in the Gastroenterology Department of 6 hospitals (Adana, Alanya, Ankara, Istanbul, Izmir, Konya) within the Baskent University Faculty of Medicine. Our study was based on the International IBD Association (IOIBD) questionnaire to evaluate the environmental risk factors in UC and CD. New adjustments and additions were made to the IOIBD questionnaire, taking into account local characteristics. Each environmental factor examined was first analyzed with a univariate and then multiple logistic regression model, the size of the estimated relative risk (odds ratio, OR) and 95% confidence interval (95% CI) for the variables were calculated. If the result of the analysis was p<0,05 it was accepted as a significant difference. As a result of multivariate analyzes, history of other infectious diseases (gastroenteritis, upper respiratory tract infection etc.) in childhood, both for UC (OR 7.56; 95% CI 1.57-36.4) and CD (OR 9.45; 95% CI 2.51-35.6) was found to be a risk factor. It has been shown that there is an inverse relationship between antibiotic use in childhood (≤15 years of age) and the risk of UC (OR 0.41; 95% CI 0.18-0.93). It has been observed that daily coffee consumption reduces the risk of both UC (OR 0.25; 95% Cl 0.15-0.42) and CD (OR 0.28; 95% CI 0.14-0.55). Increased consumption of refined sugar and industrial food products were found to be risk factors for both diseases. Stress was strongly associated with the development of UC (OR 3.27; 95% CI 1.76-6.10) and CD (OR 4.40; 95% CI 2.12-9.10). Smoking was found to increase the risk of CD (OR 2.38; 95% CI 1.16-4.91), and former smoking was found to increase the risk of UC (OR 3.16; 95% CI 1.19-8.37) with this study. Our study is the first multicenter case-control study examining the effects of environmental factors on IBD in Turkey. The protective effect of coffee consumption, stress being a risk factor, the protective effect of childhood antibiotic use on UC, and the risk factor of childhood infection-related disease are findings that were not frequently shown in other studies, and our study showed the association of these factors with IBD. In addition, the importance role of diet and smoking in the pathogenesis of IBD was emphasized once again. On the other hand, the results that may be inconsistent with other studies, has been associated with the fact that the general structure of IBD may vary according to geographical regions and different populations. The role of environmental risk factors in the development of IBD remains unclear. It is necessary to continue to carry out planned, organized and prospective studies to elucidate the effects of environmental risk factors in IBD. Key words: Ulcerative colitis, Crohn's disease, IBD, etiology, environmental factors