High incidence of inflammatory bowel disease in Northern Australia: a prospective community population-based Australian incidence study in the Mackay-Isaac-Whitsunday region

Background and AimsTo determine the incidence of inflammatory bowel disease (IBD) in the Mackay-Isaac-Whitsunday region in Northern Queensland (-21.14 degrees S) and to allow a comparison with Southern Australian and New Zealand data (Geelong, Australia -38.14 degrees S; Tasmania -41.43 degrees S and -42.88 degrees S (Launceston and Hobart) and Canterbury, New Zealand -43.46 degrees S). DesignA prospective observational community population-based IBD study was conducted between 1 June 2017 and 31 May 2018. Outcome measuresPrimary includes the crude annual incidence rate of IBD, Crohn's disease (CD), ulcerative colitis (UC) and inflammatory bowel disease-unclassified (IBDU), while secondary includes disease phenotype and behaviour. ResultsFifty-six new cases of IBD were identified. Twenty-three were CD, 30 were UC and 3 were IBDU. The crude annual incidence rate per 100 000 for IBD, CD, UC and IBDU were 32.2 (95% confidence interval (CI): 24.78-41.84), 13.23 (95% CI: 8.79-19.90), 17.25 (95% CI: 12.06-24.67) and 1.73 (95% CI: 0.56-5.35). When directly age-standardised to the World Health Organisation Standard Population Distribution, the overall CD, UC and IBDU incidence were 13.19, 17.34 and 1.85 per 100 000, with an overall age-standardised IBD incidence of 32.38. ConclusionsThis is the first study to define the incidence of IBD in a Northern Australian cohort and to allow a comparison between North and Southern Australia. The IBD crude is the highest reported in Australia. Like others, we found a high and low incidence of upper gastrointestinal Crohn's disease and complicated disease at diagnosis respectively, likely reflective of the increased availability and early uptake of endoscopic procedures.

Automated summary

This study is the first to determine the incidence of IBD in Northern Australia and compare it with Southern Australia. The crude incidence rate of IBD in Australia is the highest reported. The findings suggest a possible correlation between the increased availability and early uptake of endoscopic procedures and the higher incidence of upper gastrointestinal Crohn's disease and complicated disease at diagnosis.