Inflammatory bowel disease environmental risk factors: a population-based case-control study of Middle Eastern migration to Australia

Yanna Ko, Viraj Kariyawasam, Mohamad Karnib, Rhys Butcher, Douglas Samuel, Ahmad Alrubaie, Nabil Rahme, Charles McDonald, James Cowlishaw, Peter Katelaris, Gavin Barr, Brian Jones, Susan Connor, Gokulan Paven, Grace Chapman, Gordon Park, Richard Gearry, Rupert W. Leong*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

40 Citations (Scopus)


Background & Aims: The incidences of the inflammatory bowel diseases (IBDs) Crohn's disease (CD) and ulcerative colitis (UC) are increasing, indicating gene-environment interactions. Migrants from low-IBD-prevalence countries to a high-prevalence country may help identify the relative contribution of environmental risk factors compared with native Caucasians. Methods: This prospective case-control study evaluated IBD environmental risk factors of Middle Eastern migrants (MEM) in Australia compared with matched Caucasian IBD subjects, MEM controls, Caucasian controls, and controls in the Middle East using adjusted odds ratios (aOR). Results: A total of 795 subjects were recruited: 154 MEM cases (75 CD; 79 UC), 153 MEM controls, 162 Caucasian cases (85 CD; 77 UC), 173 Caucasian controls, and 153 controls in Lebanon. Smoking increased CD risk in MEM and Caucasians and reduced UC risk in Caucasians (aOR, 0.77; 95% CI, 0.41-0.98) but not MEM (aOR, 1.45; 95% CI, 0.80-2.62). Antibiotic use reduced the risk of MEM CD (aOR, 0.27; 95% CI, 0.11-0.67) and UC (aOR, 0.38; 95% CI, 0.18-0.80), but increased the risk in Caucasians (CD: aOR, 5.24; 95% CI, 2.13-12.90; and UC: aOR, 6.82; 95% CI, 2.67-17.38). Most hygiene markers (rural dwelling, pet ownership, pet feeding, and farm animal contact) reduced CD and UC risk in MEM (. P < .05). In contrast, in Caucasians these hygiene markers lacked significance. Other significant risk factors include IBD family history, appendectomy, tonsillectomy, and breastfeeding. Conclusions: Differential IBD environmental risk factors exist between migrants and native Caucasians, indicating a dynamic interplay between environmental factors and IBD risk for immigrants that is distinct to those factors most relevant in native Caucasians.

Original languageEnglish
Pages (from-to)1453-1463.e1
Number of pages12
JournalClinical Gastroenterology and Hepatology
Issue number8
Publication statusPublished - 1 Aug 2015
Externally publishedYes


  • Environmental
  • Hygiene hypothesis
  • Inflammatory bowel disease
  • Migrants
  • Risk factors


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