The Epidemiology of Inflammatory Bowel Disease in Oceania: A Systematic Review and Meta-Analysis of Incidence and Prevalence

Abstract Background Past studies have shown high rates of inflammatory bowel disease (IBD) in Australia and New Zealand (NZ). We aimed to describe the epidemiology of IBD in Australia, NZ, and the surrounding region (collectively termed Oceania) by conducting a systematic review and meta-analysis. Methods Electronic databases were searched from inception to April 2023 for studies reporting incidence or prevalence rates of IBD, Crohn’s disease (CD), or ulcerative colitis (UC) in Oceania. All study designs were included. A meta-analysis calculated pooled estimates of incidence and prevalence, and a sensitivity analysis compared the pooled population-based studies with the non–population-based studies and the Australian and NZ studies separately. Results Nineteen incidence and 11 prevalence studies were included; 2 studies were from the Pacific Islands, with the rest coming from Australia and NZ. Pooled estimates showed high incidence rates of 19.8 (95% confidence interval [CI], 15.8-23.7) for IBD, 8.3 (95% CI, 6.9-9.8) for CD, and 7.4 (95% CI, 5.7-9.1) for CD per 100 000 person-years. CD was more common than UC in most studies. The pooled estimates for the prevalence studies were 303.3 (95% CI, 128.1-478.4) for IBD, 149.8 (95% CI, 71.0-228.5) for CD, and 142.2 (95% CI, 63.1-221.4) for UC per 100 000 persons. Studies using population-based data collection methods showed higher pooled rates for both incidence and prevalence. Conclusions The incidence and prevalence of IBD in Oceania is high. The studies were heterogeneous and there were several geographic areas with no information, highlighting the need for more epidemiological studies of IBD. Lay Summary This systematic review and meta-analysis of inflammatory bowel disease in Oceania found high incidence rates (19.8 [95% confidence interval, 15.8-23.7] per 100 000 person-years) and prevalence rates (303.3 [95% confidence interval, 128.1-478.4] per 100 000 persons). Most studies were from Australasia, with only 2 from the Pacific Islands.