Aim
To describe the incidence and phenotype of IBD and distribution within ethnic groups.

Methods
Adult patients (>16 years) with newly diagnosed IBD (fulfilling Copenhagen diagnostic criteria) were prospectively recruited over one year in 5 urban catchment areas with high South Asian population. Patient demographics, ethnic codes, disease phenotype (Montreal classification), disease activity and treatment within 3 months of diagnosis were recorded onto the Epicom database.
Results

Across a population of 2,271,406 adults, 339 adult patients were diagnosed with IBD over one year: 218 with UC (64.3%), 115 with CD (33.9%) and 6 with IBDU (1.8%). The crude incidence of IBD, UC and CD was 17.0/100,000, 11.3/100,000 and 5.3/100,000 respectively. The age adjusted incidence of IBD and UC were significantly higher in the Indian group (25.2.100,000 and 20.5/100,000) compared to White European (14.9/100,000, p=0.009 and 8.2/100,000, p<0.001) and Pakistani groups (14.9/100,000, p=0.001 and 11.2/100,000, p=0.007). The Indian group were significantly more likely to have extensive disease than White Europeans (52.7% vs 41.7%, p=0.031). There was no significant difference in time to diagnosis, disease activity and treatment.

Conclusions

This is the only prospective study to report the incidence of IBD in an ethnically diverse UK population. The Indian ethnic group showed the highest age-adjusted incidence of UC (20.5/100,000). Further studies on dietary, microbial and metabolic factors that might explain these findings in UC are underway.
KEYWORDS: Inflammatory bowel disease, Ethnicity, Epidemiology, Incidence, Phenotype

Core tip: We performed a UK multicentre prospective cohort study to describe the incidence of IBD and differences within ethnic groups. Seven urban centres with high ethnic background population recruited 339 cases over a 1 year period. Patients of Indian ethnicity were almost three times more likely to have UC than White Europeans. The impact of diet and environmental factors on this high risk population requires further study.