Rising Incidence of Paediatric Inflammatory Bowel Disease in Canterbury, New Zealand, 1996-2015

Background: The incidence of paediatric inflammatory bowel disease (IBD) around the world is increasing. Canterbury, New Zealand, has one of the highest Crohn disease (CD) incidence rates published. The present study aimed to document the incidence of paediatric IBD in Canterbury between 1996 and 2015. Methods: All patients diagnosed with IBD in Canterbury, while younger than 16 years, between January 1, 1996 and December 31, 2015 were identified. Demographic and disease phenotypic details were collected and entered into a secure database. Age-specific population data for Canterbury were obtained and annual incidence rates were then calculated. Results: The mean annual incidence rate over the 20-year period was 7.18/100,000 (95% confidence interval 5.55-8.81) children. There was a 4-fold increase in the incidence of paediatric IBD in Canterbury between 1996 and 2015. The ratio of CD to ulcerative colitis (UC) diagnosed was 8.4:1. Disease phenotype of CD and UC, based on the Paris classification, were comparable with other studies. Conclusions: The incidence of paediatric IBD in Canterbury has increased dramatically during the last 2 decades. Some of the observed incidence rates are among the highest documented anywhere in the world. The preponderance of CD over UC in the present study is the highest published.