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Original article
Environmental risk factors in inflammatory bowel disease: a population-based case-control study in Asia-Pacific
  1. Siew C Ng1,
  2. Whitney Tang1,
  3. Rupert W Leong2,
  4. Minhu Chen3,
  5. Yanna Ko2,
  6. Corrie Studd4,
  7. Ola Niewiadomski4,
  8. Sally Bell4,
  9. Michael A Kamm4,5,
  10. H J de Silva6,
  11. Anuradhani Kasturiratne6,
  12. Yasith Udara Senanayake6,
  13. Choon Jin Ooi7,
  14. Khoon-Lin Ling7,
  15. David Ong8,
  16. Khean Lee Goh9,
  17. Ida Hilmi9,
  18. Qin Ouyang10,
  19. Yu-Fang Wang10,
  20. PinJin Hu3,
  21. Zhenhua Zhu3,
  22. Zhirong Zeng3,
  23. Kaichun Wu11,
  24. Xin Wang11,
  25. Bing Xia12,
  26. Jin Li12,
  27. Pises Pisespongsa13,
  28. Sathaporn Manatsathit14,
  29. Satimai Aniwan15,
  30. Marcellus Simadibrata16,
  31. Murdani Abdullah16,
  32. Steve W C Tsang17,
  33. Tai Chiu Wong18,
  34. Aric J Hui19,
  35. Chung Mo Chow20,
  36. Hon Ho Yu21,
  37. Mo Fong Li21,
  38. Ka Kei Ng22,
  39. Jessica Ching1,
  40. Justin C Y Wu1,
  41. Francis K L Chan1,
  42. Joseph J Y Sung1
  43. on behalf of the Asia-Pacific Crohn's and Colitis Epidemiology Study (ACCESS) Group
  1. 1Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Institute of Digestive Disease, Li Ka Shing Institute of Health Science, Hong Kong, China
  2. 2Bankstown and Concord Hospitals, Sydney, New South Wales, Australia
  3. 3The First Affiliated Hospital of San Yat Sen University, Guangzhou, China
  4. 4St Vincent's Hospital, University of Melbourne, Melbourne, Victoria, Australia
  5. 5Imperial College London, London, UK
  6. 6Faculty of Medicine, University of Kelaniya, Ragama, Sri Lanka
  7. 7Singapore General Hospital, Singapore, Singapore
  8. 8National University Hospital of Singapore, Singapore, Singapore
  9. 9University of Malaya Medical Center, Kuala Lumpur, Malaysia
  10. 10West China Hospital, Sichuan University, Chengdu, China
  11. 11Xijing Hospital, Fourth Military Medical University, Xian, China
  12. 12Zhongnan Hospital of Wuhan University, Wuhan, China
  13. 13Maharaj Nakorn Chiangmai Hospital, Chiangmai, Thailand
  14. 14Siriraj Hosptial, Bangkok, Thailand
  15. 15King Chulalongkorn Memorial Hospital, Bangkok, Thailand
  16. 16University of Indonesia, Indonesia, Indonesia
  17. 17Tseung Kwan O Hospital, Hong Kong, Hong Kong
  18. 18North District Hospital, Hong Kong, Hong Kong
  19. 19Alice Ho Miu Ling Nethersole Hospital, Hong Kong, Hong Kong
  20. 20Department of Pediatrics, Chinese University of Hong Kong, Hong Kong, Hong Kong
  21. 21Kiangwu Hospital, Macao, China
  22. 22Hospital Conde S Januario, Macau, China
  1. Correspondence to Dr Siew C Ng, Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Institute of Digestive Disease, Li Ka Shing Institute of Health Science, Chinese University of Hong Kong, Hong Kong, China; siewchienng{at}


Objective The rising incidence of inflammatory bowel disease in Asia supports the importance of environmental risk factors in disease aetiology. This prospective population-based case-control study in Asia-Pacific examined risk factors prior to patients developing IBD.

Design 442 incident cases (186 Crohn's disease (CD); 256 UC; 374 Asians) diagnosed between 2011 and 2013 from eight countries in Asia and Australia and 940 controls (frequency-matched by sex, age and geographical location; 789 Asians) completed an environmental factor questionnaire at diagnosis. Unconditional logistic regression models were used to estimate adjusted ORs (aOR) and 95% CIs.

Results In multivariate model, being breast fed >12 months (aOR 0.10; 95% CI 0.04 to 0.30), antibiotic use (aOR 0.19; 0.07 to 0.52), having dogs (aOR 0.54; 0.35 to 0.83), daily tea consumption (aOR 0.62; 0.43 to 0.91) and daily physical activity (aOR 0.58; 0.35 to 0.96) decreased the odds for CD in Asians. In UC, being breast fed >12 months (aOR 0.16; 0.08 to 0.31), antibiotic use (aOR 0.48; 0.27 to 0.87), daily tea (aOR 0.63; 0.46 to 0.86) or coffee consumption (aOR 0.51; 0.36 to 0.72), presence of hot water tap (aOR 0.65; 0.46 to 0.91) and flush toilet in childhood (aOR 0.71; 0.51 to 0.98) were protective for UC development whereas ex-smoking (aOR 2.02; 1.22 to 3.35) increased the risk of UC.

Conclusions This first population-based study of IBD risk factors in Asia-Pacific supports the importance of childhood immunological, hygiene and dietary factors in the development of IBD, suggesting that markers of altered intestinal microbiota may modulate risk of IBD later in life.

  • IBD

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