Inflammatory bowel disease incidence, prevalence and twelve-month initial disease course in Tasmania, Australia

Background: High inflammatory bowel disease (IBD) rates have been reported in Australasia, but no state-wide studies have yet been performed.

Aims: This study estimates the one-year incidence and point prevalence of IBD in the state of Tasmania, Australia. It also reports clinical outcomes after twelve months of diagnosis in an incident cohort.

Methods: A prospective, population-based study was performed collecting prevalent and incident state-wide cases from 1st June 2013 to 31st May 2014. Case data were identified from specialist doctors, pathology databases and hospital records. Age-standardised rates (ASRs) were calculated based on World Health Organization 2000 standard population characteristics. Incident cases were followed up twelve months after diagnosis.

Results: There were 1719 prevalent cases: ASRs for IBD, Crohn's disease (CD), ulcerative colitis (UC) and inflammatory bowel disease unclassified (IBDU) prevalence were 303.9, 165.5, 131.4 and 6.9 per 100,000 respectively. Prevalent CD cases were younger, with greater immunomodulator/biologic use and bowel resections. There were 149 incident cases: ASRs for IBD, CD, UC and IBDU incidence were 29.5, 15.4, 12.4, and 1.7 per 100,000 respectively. Incident CD cases were more likely than UC or IBDU to require escalation of medical therapy, hospitalisation, and bowel resection especially among those with penetrating or stricturing disease. They had longer duration of symptoms prior to diagnosis.

Conclusions: IBD prevalence and incidence rates are high in Tasmania, comparable to data from other Australasian studies and those from Northern Europe and America. Poorer twelve month clinical outcomes occurred in complicated CD, with greater use of healthcare resources.