title: Association between early-life factors and risk of child-onset Crohn's disease among Victorian children born 1983-1998: a birth cohort study.
abstract: BACKGROUND
  The incidence of Crohn's disease (CD) with onset before age 16 has increased. Several perinatal characteristics have been associated with CD. Our objective was to examine the temporal change in CD incidence by period of birth and the extent that this could be attributed to perinatal characteristics associated with higher CD risk.
  
  
  METHODS
  A record linkage study was conducted utilizing the perinatal records of Victorian births 1983-1998 inclusive and a state-based CD registry. Proportional hazards models were used to investigate the perinatal factors in relation to the onset of CD by age 16. Further, a nested case control study was conducted to examine the association between sibling exposure and CD risk.
  
  
  RESULTS
  The CD incidence rate for births 1983-1998 was 2.01 (95% confidence interval [CI] 1.79, 2.27) per 100,000 child-years. A birth cohort effect was demonstrated, with higher CD risk for 1992-1998 versus 1983-1991 births (hazard ratio [HR] 1.56; 95% CI 1.18, 2.06). Perinatal characteristics associated with higher CD risk included urban location, higher socioeconomic status, married mother, a congenital abnormality and delivery by elective cesarean section. Sibling exposure during the first 6 years of life was not associated with CD risk. The increased CD incidence among more recent births was not accounted for by changes in these measured perinatal factors.
  
  
  CONCLUSIONS
  The temporal increase in CD incidence documented for births up to 1990 has continued for children born after 1991 and was not accounted for by temporal changes in the measured perinatal factors.
authors.affiliation: Murdoch Childrens Research Institute, Royal Childrens Hospital, Melbourne, Victoria, Australia. anne-louise.ponsonby@mcri.edu.au
authors.forename: Anne-Louise
authors.initials: AL
authors.lastname: Ponsonby
authors.forename: Anthony G
authors.initials: AG
authors.lastname: Catto-Smith
authors.forename: Angela
authors.initials: A
authors.lastname: Pezic
authors.forename: Sandy
authors.initials: S
authors.lastname: Dupuis
authors.forename: Jane
authors.initials: J
authors.lastname: Halliday
authors.forename: Don
authors.initials: D
authors.lastname: Cameron
authors.forename: Ruth
authors.initials: R
authors.lastname: Morley
authors.forename: John
authors.initials: J
authors.lastname: Carlin
authors.forename: Terry
authors.initials: T
authors.lastname: Dwyer
mesh_terms: D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D016022:Case-Control Studies; D002585:Cesarean Section / Q000706:statistics & numerical data; D002648:Child; D015331:Cohort Studies; D003424:Crohn Disease / Q000453:epidemiology*; D004522:Educational Status; D005192:Family Health; D005260:Female; D006801:Humans; D015994:Incidence; D007231:Infant, Newborn; D008297:Male; D008423:Maternal Age; D016016:Proportional Hazards Models; D012042:Registries; D012307:Risk Factors; D035781:Siblings; D014739:Victoria / Q000453:epidemiology; D055815:Young Adult