title: Identification of Environmental Factors Associated with Inflammatory Bowel Disease in a Southwestern Highland Region of China: A Nested Case-Control Study.
abstract: BACKGROUND
  The aim of this study was to examine environmental factors associated with inflammatory bowel disease (IBD) in Yunnan Province, a southwestern highland region of China.
  
  
  METHODS
  In 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).
  
  
  RESULTS
  A 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).
  
  
  CONCLUSIONS
  This 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.
authors.affiliation: Department of Gastroenterology, The First Affiliated Hospital of Kunming Medical University, Yunnan Institute of Digestive Disease, Kunming, Yunnan Province, P. R. China.
authors.forename: Junkun
authors.initials: J
authors.lastname: Niu
authors.affiliation: Department of Gastroenterology, The First Affiliated Hospital of Kunming Medical University, Yunnan Institute of Digestive Disease, Kunming, Yunnan Province, P. R. China.
authors.forename: Jiarong
authors.initials: J
authors.lastname: Miao
authors.affiliation: Department of Gastroenterology, The First People's Hospital of Qujing, Qujing, Yunnan Province, P. R. China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Tang
authors.affiliation: Department of Gastroenterology, The First Affiliated Hospital of Kunming Medical University, Yunnan Institute of Digestive Disease, Kunming, Yunnan Province, P. R. China.
authors.forename: Qiong
authors.initials: Q
authors.lastname: Nan
authors.affiliation: Department of Gastroenterology, The First Affiliated Hospital of Kunming Medical University, Yunnan Institute of Digestive Disease, Kunming, Yunnan Province, P. R. China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Department of Gastroenterology, The First Affiliated Hospital of Kunming Medical University, Yunnan Institute of Digestive Disease, Kunming, Yunnan Province, P. R. China.
authors.forename: Gang
authors.initials: G
authors.lastname: Yang
authors.affiliation: Department of Gastroenterology, The First Affiliated Hospital of Kunming Medical University, Yunnan Institute of Digestive Disease, Kunming, Yunnan Province, P. R. China.
authors.forename: Xiangqian
authors.initials: X
authors.lastname: Dong
authors.affiliation: Department of Gastroenterology, The First Affiliated Hospital of Kunming Medical University, Yunnan Institute of Digestive Disease, Kunming, Yunnan Province, P. R. China.
authors.forename: Qi
authors.initials: Q
authors.lastname: Huang
authors.affiliation: Department of Gastroenterology, The First Affiliated Hospital of Kunming Medical University, Yunnan Institute of Digestive Disease, Kunming, Yunnan Province, P. R. China.
authors.forename: Shuxian
authors.initials: S
authors.lastname: Xia
authors.affiliation: Department of General Surgery, The First Affiliated Hospital of Kunming Medical University, Yunnan Institute of Digestive Disease, Kunming, Yunnan Province, P. R. China.
authors.forename: Kunhua
authors.initials: K
authors.lastname: Wang
authors.affiliation: Department of Gastroenterology, The First Affiliated Hospital of Kunming Medical University, Yunnan Institute of Digestive Disease, Kunming, Yunnan Province, P. R. China.
authors.forename: Yinglei
authors.initials: Y
authors.lastname: Miao
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D002681:China / Q000453:epidemiology; D003093:Colitis, Ulcerative / Q000453:epidemiology*; D003424:Crohn Disease / Q000453:epidemiology*; D004777:Environment; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011795:Surveys and Questionnaires