P669 Inflammatory Bowel Disease is prevalent in Australia but rare in Indigenous Australians
G. Iyngkaran1, J. Hunt2, T. Thambimuthu*2, M. Bottolfsen2, E. Tse3, S. Sivanesan1, D. Liew4
1Royal Melbourne Hospital, Colorectal Medicine and Genetics, Parkville, Australia, 2Royal Darwin Hospital, Medicine, Darwin, Australia, 3Royal Adelaide Hospital, Medicine, Adelaide, Australia, 4Royal Melbourne Hospital, Medicine, Parkville, Australia
The incidence of inflammatory bowel disease (IBD) has risen dramatically in Western countries since the 1950s, with the highest rates observed in North America and Western Europe. In Canada, there is a significantly lower incidence of IBD in rural Aboriginal communities. Although this may be due to under-diagnosis, genetics and changing environmental exposures may also be factors. A lower risk of developing IBD has been reported in developing countries, rural communities, poor socioeconomic groups, overcrowded communities and in areas lacking clean or hot water. These factors are found in rural Indigenous communities in the Northern Territory (NT) of Australia. The incidence of IBD in urban Australia is comparable to Western Europe  but limited data is available for Indigenous Australians (IA).
The Royal Darwin Hospital is the only tertiary referral centre in the NT and all IBD patients are referred to its Gastroenterology service. The hospital's database was searched for all patients who presented with IBD from 2007-14. Prospective data was collected from 2013. Population demographic data were drawn from the Australian Bureau of Statistics.
In 2013, there were 212,651 individuals residing in the NT, including 64,560 IA. In 2007-2014, 279 patients with IBD were treated at the Royal Darwin Hospital, equating to a period prevalence of 131 per 105. The prevalences (per 105) of various types of IBD were: ulcerative colitis (UC) 62, Crohn's Disease (CD) 67 and indeterminant colitis 2. Notably, only 3 patients with IBD were IA (all of mixed race), meaning to a prevalence of 5 per 105 among IA. The specific prevalence among the non-IA population was 186 per 105. The NT population residing outside of the capital city comprised 76,406 individuals, of whom 49457 were IA. Of the 279 IBD patients, only 2 resided rurally (1 IA and 1 non-IA). Hence the period prevalence of IBD was 3 per 105 in the non-urban population and 203 per 105 in the urban population. In 2013 the incidence of IBD was 20 (UC 9, CD 11) per 105 with no cases in the IA population.
This is the first epidemiological study of IBD in Australia that includes IA. Mindful of the small samples in some subgroups, it suggests a high prevalence of IBD in the non IA urban population but a very low prevalence among IA and people living in non-urban areas. This may be due to genetic or environmental factors. For example, a previous study has shown differences in gut microbial profiles in IA compared to Caucasian controls .
 Bernstein C, Shanahan F, (2008), Disorders of a modern lifestyle: reconciling the epidemiology of inflammatory bowel diseases. , Gut, 1185-91
 Loftus EV Jr. , (2004), Clinical epidemiology of inflammatory bowel disease: incidence, prevalence, and environmental influences. , Gastroenterology, 1504-17
 Manichanh C, Borruel N, (2012), The gut microbiota in IBD, Nat Rev Gastroenterol Hepatol, 599-608
 Wilson, J., et al., (2010), High incidence of inflammatory bowel disease in Australia: a prospective population-based Australian incidence study, IBD, 1550-6
 Iyngkaran G, Sivanesan S, Kang S et al, (2013), Indigenous Australians have a distinctive gut microbial profile compared to patients with inflammatory bowel disease and non Indigenous controls, European Crohns and Colitis Vienna 2013