The South Asian inflammatory bowel disease (IBD) phenotype: ethnic differences demonstrated through analysis of the UK IBD BioResource database

Introduction

South Asians (SA) living in the West have a high incidence of IBD, yet knowledge of IBD clinical phenotypes in SA is limited. We evaluated phenotypic differences between SA and white IBD patients recruited into the UK IBD BioResource.

Methods

We conducted a multi-centre analysis of prospectively collected data from the UK IBD BioResource. Participants of SA or W ethnicity were included. χ² and Mann-Whitney U testing were used to analyse categorical and continuous variables respectively. Post hoc testing of the standardised residuals was done for significant variables with more than two classes, and P values adjusted for multiple comparisons using Benjamini-Hochberg.

Results

29,728 individuals with confirmed IBD were included (47.9% CD, 45.7% UC and 6.5% IBD-U). UC was predominant in SA (SA 59.0% vs white 45.2%, p_adj <0.0001) and CD in white (white 48.4% vs SA 33.7%, p_adj <0.0001).

UC

12,950 (95.4%) UC patients were white and 630 (4.6%) SA. There was a male predominance in SA (58.7% male, 41.3% female); sex distribution in white patients was even (50.2% male, 49.8% female; p <0.001). SA were younger at diagnosis [29 (IQR 22–38) vs 35 (IQR 25–49) years, p <0.001]. SA were more likely never to have smoked (SA 77.4% vs white 46.3%, p_adj <0.0001). Fewer SA had proctitis (SA 12.5% vs white 17.7%, p = 0.005) and more had extensive disease (SA 41.7% vs white 34.3%, p <0.001). There was no difference in the need for colectomy (SA 5.5% vs white 5.6%, p=0.967).

CD

13,476 (97.5%) CD patients were white and 341 (2.5%) SA. There was a male predominance in SA (62.2% male, 37.8% female) and female in white patients (44.8% male, 55.2% female). The median age of diagnosis was similar [SA 25 (IQR 17–37) vs white 26 (19–39) years, p=0.015]. SA were more likely never to have smoked (SA 71.4% vs white 45.4%, p_adj <0.0001). SA were less likely to have stricturing (SA 17.0% vs white 25.7%, p_adj 0.0006) or penetrating (SA 9.3% vs white 13.0%, p_adj 0.048) disease. There was no difference in disease location, but fewer SA required surgery (SA 34.7% vs white 51.2%, p <0.001). There were no differences in prevalence of extra-intestinal manifestations (EIMs) in UC or CD.

Conclusions

We have demonstrated distinct demographic and phenotypic characteristics in SA IBD patients. Particular genetic, environmental and behavioural factors may confer ethnicity-specific IBD phentotypes, potentially influencing IBD management in such cohorts.