title: Epidemiology of inflammatory bowel disease: Is there a shift towards onset at a younger age?
abstract: OBJECTIVE
  Increasing numbers of paediatric and adolescent patients with Crohn disease (CD) and ulcerative colitis (UC) are reported. To determine whether this observation is a consequence of a shift towards onset at a younger age, we analysed retrospective data from patients enrolled in the Swiss IBD Cohort Study (SIBDCS).
  
  
  METHODS
  The SIBDCS is a disease-based cohort in Switzerland, which collects retrospective and prospective data on a large sample of patients with inflammatory bowel disease (IBD). Patients, diagnosed from 1980, were stratified according to diagnosis of CD and UC. Age at disease onset (age at first symptoms and age at diagnosis) was analysed in relation to calendar year of disease onset. Data were extracted from physician and patient questionnaires. Linear regressions of age at disease onset by calendar year of disease onset adjusted by sex, country of birth, and education were performed.
  
  
  RESULTS
  Adjusted regression coefficients for CD and UC were significantly positive, that is, age at disease onset has increased with time. Male sex was associated with an increase in age at disease onset, and birth in Switzerland with a decrease. These associations were statistically significant.
  
  
  CONCLUSIONS
  The results from the SIBDCS do not support the hypothesis that disease onset of both CD and UC occur today at a younger age. On the contrary, our results show that there is a significant trend for age at disease onset occurring at an older age today as compared with recent decades. We conclude that the observation of increasing numbers of paediatric and adolescent patients with IBD is not caused by a trend towards disease onset at a younger age, but that this may rather be a consequence of the overall increasing incidence of these conditions.
authors.affiliation: Division of Gastroenterology and Nutrition, University Children's Hospital Zurich, Zurich, Switzerland. christian.braegger@kispi.uzh.ch
authors.forename: Christian P
authors.initials: CP
authors.lastname: Braegger
authors.forename: Pierluigi
authors.initials: P
authors.lastname: Ballabeni
authors.forename: Daniela
authors.initials: D
authors.lastname: Rogler
authors.forename: Stephan R
authors.initials: SR
authors.lastname: Vavricka
authors.forename: Michael
authors.initials: M
authors.lastname: Friedt
authors.forename: Valérie
authors.initials: V
authors.lastname: Pittet
mesh_terms: D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D002648:Child; D015331:Cohort Studies; D003424:Crohn Disease / Q000453:epidemiology; D005260:Female; D019456:Health Transition; D006801:Humans; D015212:Inflammatory Bowel Diseases / Q000453:epidemiology*; D008297:Male; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012737:Sex Factors; D011795:Surveys and Questionnaires; D013557:Switzerland / Q000453:epidemiology; D055815:Young Adult