title: Inflammatory bowel disease in immigrants to Canada and their children: a population-based cohort study.
abstract: OBJECTIVE
  The risk of inflammatory bowel disease (IBD) contributed by the environment can be elucidated by assessing the risk in migrants from low prevalence to Western countries. The incidence of IBD in immigrants to Canada and their Canadian-born children was compared with nonimmigrants.
  
  
  METHODS
  A population-based cohort of IBD patients derived from health administrative data was linked to immigration data to determine the standardized incidence of IBD in immigrants to Ontario, Canada, by region of birth between 1994 and 2010. The hazard contributed by younger age at immigration was determined. Incidence for Ontario-born children of immigrant mothers was compared with the children of nonimmigrants.
  
  
  RESULTS
  In 2,144,660 immigrants, incidence of IBD was 7.3/100,000 person-years compared with 23.9/100,000 in 12,036,921 nonimmigrants (incidence rate ratio (IRR) 0.34, 95% CI 0.26-0.44). Incidence was lowest risk in East Asians (IRR 0.14, 95% CI 0.11-0.18) and highest in Western Europeans/North Americans (IRR 0.59, 95% CI 0.46-0.75). Increased age at immigration was associated with decreased risk of IBD (HR 0.986, 95% CI 0.982-0.990), a 14% increased risk per younger decade of life at immigration. Children of immigrants from the Middle East/North Africa, South Asia, Sub-Saharan Africa, and North America/Western Europe had similar risk of IBD as children of nonimmigrants; however, the incidence remained lower among children of immigrants from other regions.
  
  
  CONCLUSIONS
  Younger age at arrival to Canada increased the risk of IBD in immigrants. Canadian-born children of immigrants from some regions assumed the high Canadian incidence of IBD, indicating that the underlying risk is activated with earlier life exposure to the Canadian environment in certain groups.
authors.affiliation: 1] Division of Gastroenterology, Hepatology and Nutrition, Children's Hospital of Eastern Ontario IBD Centre, Children's Hospital of Eastern Ontario, Ottawa, Ontario, Canada [2] Department of Pediatrics, University of Ottawa, Ottawa, Ontario, Canada [3] School of Epidemiology, Public Health and Preventative Medicine, University of Ottawa, Ottawa, Ontario, Canada [4] Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada.
authors.forename: Eric I
authors.initials: EI
authors.lastname: Benchimol
authors.affiliation: 1] Division of Gastroenterology, Hepatology and Nutrition, Children's Hospital of Eastern Ontario IBD Centre, Children's Hospital of Eastern Ontario, Ottawa, Ontario, Canada [2] Department of Pediatrics, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: David R
authors.initials: DR
authors.lastname: Mack
authors.affiliation: 1] Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada [2] Department of Paediatrics, Division of General Paediatrics, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Astrid
authors.initials: A
authors.lastname: Guttmann
authors.affiliation: 1] Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada [2] Department of Medicine, Mount Sinai Centre for Inflammatory Bowel Disease, Mount Sinai Hospital, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Geoffrey C
authors.initials: GC
authors.lastname: Nguyen
authors.affiliation: 1] Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada [2] Child Health Evaluative Sciences, The Hospital for Sick Children, Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Teresa
authors.initials: T
authors.lastname: To
authors.affiliation: Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada.
authors.forename: Nassim
authors.initials: N
authors.lastname: Mojaverian
authors.affiliation: 1] Division of Gastroenterology, Hepatology and Nutrition, Children's Hospital of Eastern Ontario IBD Centre, Children's Hospital of Eastern Ontario, Ottawa, Ontario, Canada [2] Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada.
authors.forename: Pauline
authors.initials: P
authors.lastname: Quach
authors.affiliation: 1] Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada [2] Ottawa Hospital Research Institute, Ottawa, Ontario, Canada [3] Department of Family Medicine, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Douglas G
authors.initials: DG
authors.lastname: Manuel
mesh_terms: D000293:Adolescent; D000328:Adult; D017954:Africa South of the Sahara / Q000208:ethnology; D000352:Africa, Northern / Q000208:ethnology; D000367:Age Factors; D044466:Asian People / Q000706:statistics & numerical data*; D044383:Black People / Q000706:statistics & numerical data*; D015331:Cohort Studies; D054242:Emigrants and Immigrants / Q000706:statistics & numerical data*; D005060:Europe / Q000208:ethnology; D005260:Female; D006801:Humans; D015994:Incidence; D015212:Inflammatory Bowel Diseases / Q000453:epidemiology* / Q000208:ethnology; D008297:Male; D008875:Middle Aged; D008877:Middle East / Q000208:ethnology; D009656:North America / Q000208:ethnology; D009864:Ontario / Q000453:epidemiology; D016016:Proportional Hazards Models; D012111:Residence Characteristics; D012189:Retrospective Studies; D012306:Risk; D044465:White People / Q000706:statistics & numerical data*; D055815:Young Adult