title: Population-based cases control study of inflammatory bowel disease risk factors.
abstract: OBJECTIVE
  The rapid increase in inflammatory bowel disease (IBD) incidence confirms the importance of environment in its etiology. We aimed to assess the role of childhood and other environmental risk factors in IBD.
  
  
  METHODS
  A population-based case-control study was carried out in Canterbury, New Zealand. Participants comprised 638 prevalent Crohn's disease (CD) cases, 653 prevalent ulcerative colitis (UC) cases and 600 randomly-selected sex and age matched controls. Exposure rates to environmental risk factors were compared. Unadjusted and adjusted odds ratios (OR) with 95% confidence intervals (CI) are presented.
  
  
  RESULTS
  A family history of IBD (CD OR 3.06 [2.18-4.30], UC OR 2.52 [1.90-3.54]), cigarette smoking at diagnosis (CD OR 1.99 [1.48-2.68], UC OR 0.67 [0.48-0.94]), high social class at birth (CD and UC trend, P < 0.001) and Caucasian ethnicity (CD OR 2.04 [1.05-4.38], UC OR 1.47 [1.01-2.14]) were significantly associated with IBD. City living was associated with CD (P < 0.01). Being a migrant was associated with UC (UC OR 1.40 [1.14-2.01]). Having a childhood vegetable garden was protective against IBD (CD OR 0.52 [0.36-0.76], UC OR 0.65 [0.45-0.94]) as was having been breast-fed (CD OR 0.55 [0.41-0.74], UC OR 0.71 [0.52-0.96]) with a duration-response effect. Appendicectomy, tonsillectomy, infectious mononucleosis and asthma were more common in CD patients than controls (P < 0.01).
  
  
  CONCLUSIONS
  The importance of childhood factors in the development of IBD is confirmed. The duration-response protective association between breast-feeding and subsequent development of IBD requires further evaluation, as does the protective effect associated with a childhood vegetable garden.
authors.affiliation: Department of Medicine, University of Otago, Christchurch, New Zealand. Richard.gearry@cdhb.govt.nz
authors.forename: Richard B
authors.initials: RB
authors.lastname: Gearry
authors.forename: Ann K
authors.initials: AK
authors.lastname: Richardson
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Frampton
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Dodgshun
authors.forename: Murray L
authors.initials: ML
authors.lastname: Barclay
mesh_terms: D000328:Adult; D001062:Appendectomy / Q000009:adverse effects; D001249:Asthma / Q000150:complications / Q000453:epidemiology; D001942:Breast Feeding / Q000453:epidemiology; D016022:Case-Control Studies; D003093:Colitis, Ulcerative / Q000453:epidemiology* / Q000209:etiology* / Q000517:prevention & control; D003424:Crohn Disease / Q000453:epidemiology* / Q000209:etiology* / Q000517:prevention & control; D004777:Environment; D005260:Female; D051639:Gardening; D020022:Genetic Predisposition to Disease; D006801:Humans; D006920:Hygiene; D015994:Incidence; D007244:Infectious Mononucleosis / Q000150:complications / Q000453:epidemiology; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009520:New Zealand / Q000453:epidemiology; D016017:Odds Ratio; D010375:Pedigree; D011159:Population Surveillance; D012111:Residence Characteristics; D018570:Risk Assessment; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects / Q000453:epidemiology; D012923:Social Class; D011795:Surveys and Questionnaires; D014068:Tonsillectomy / Q000009:adverse effects; D014171:Transients and Migrants; D014504:Urban Health; D044465:White People / Q000706:statistics & numerical data; D055815:Young Adult