Identification of Environmental Factors Associated with Inflammatory Bowel Disease in a Southwestern Highland Region of China: A Nested Case-Control Study

Abstract

BackgroundThe aim of this study was to examine environmental factors associated with inflammatory bowel disease (IBD) in Yunnan Province, a southwestern highland region of China.MethodsIn this nested case-control study, newly diagnosed ulcerative colitis (UC) cases in 2 cities in Yunnan Province and Crohn’s disease (CD) cases in 16 cities in Yunnan Province were recruited between 2008 and 2013. Controls were matched by geography, sex and age at a ratio of 1:4. Data were collected using the designed questionnaire. Conditional logistic regression models were used to estimate adjusted odds ratios (ORs).ResultsA total of 678 UC and 102 CD cases were recruited. For UC, various factors were associated with an increased risk of developing UC: dietary habits, including frequent irregular meal times; consumption of fried foods, salty foods and frozen dinners; childhood factors, including intestinal infectious diseases and frequent use of antibiotics; and other factors, such as mental labor, high work stress, use of non-aspirin non-steroidal anti-inflammatory drugs and allergies (OR > 1, p < 0.05). Other factors showed a protective effect: such as consumption of fruits, current smoking, physical activity, and drinking tea (OR < 1, p < 0.05). For CD, appendectomy and irregular meal times increased the disease risk (OR >1, p < 0.05), whereas physical activity may have reduced this risk (OR < 1, p < 0.05).ConclusionsThis study is the first nested case-control study to analyze the association between environmental factors and IBD onset in a southwestern highland region of China. Certain dietary habits, lifestyles, allergies and childhood factors may play important roles in IBD, particularly UC.

Emerging trends of inflammatory bowel disease in South Korea: A nationwide population‐based study

“…In addition, fresh food and vegetable consumption remains low, and dining out has grown substantially, especially among young singles (KOSIS, http://kosis.kr/). These dietary and lifestyle factors, linked to industrialization, may increase the risk of IBD, particularly for those exposed to these determinants at an early age . However, further studies are needed to assess the changes in IBD incidence to confirm this hypothesis.…”

“…These dietary and lifestyle factors, linked to industrialization, may increase the risk of IBD, particularly for those exposed to these determinants at an early age. 28,29 However, further Epidemiology of IBD in Korea studies are needed to assess the changes in IBD incidence to confirm this hypothesis.…”

Smoking and Inflammatory Bowel Disease: A Comparison of China, India, and the USA

“…Our findings were also partly similar to those in a case-control study published in 2015, which studied 374 incident IBD cases and 789 neighborhood controls in 8 regions in Asia, which found that former smoking was associated with an increased risk of UC in Asians (aOR [95% CI] 2.0 [1.2–3.4]), while neither current nor former smoking was significantly associated with CD [24]. Two other Chinese studies also found former smoking to be a risk factor for UC [25]. Few Asian studies have examined the impact of smoking on IBD outcomes.…”

Smoking influences the need for surgery in patients with the inflammatory bowel diseases: a systematic review and meta-analysis incorporating disease duration

“…The association between smoking and surgery could be influenced by age at diagnosis, disease location, disease behaviour, and/or medications used to treat IBD. Further, ethnic differences may play an additional role on this association, with recent evidence suggesting that the impact of smoking on the development of Crohn’s disease varies across ethnicities [29, 30]. Secondly, selection bias in defining the study populations may have introduced bias in our analyses.…”