Comorbid immune-mediated diseases in inflammatory bowel disease: a nation-wide population-based study

Background: Although a higher risk of other immune-mediated diseases has been reported in inflammatory bowel disease (IBD) patients, the risk factors of immune-mediated diseases development and the effect of concomitant immune-mediated diseases on outcomes remain poorly defined. Aim: To determine the risk factors of incident immune-mediated diseases and the impact of comorbid immune-mediated diseases on outcomes in IBD. Methods: Using the National Health Insurance claims data for the entire Korean population, we identified 35 581 IBD patients without immune-mediated diseases and 595 IBD patients with immune-mediated diseases from 2012 to 2013, and follow-up until 2016. We selected four controls by age and sex for comparing with cases. Results: A total of 35 581 IBD patients without immune-mediated diseases and 142 324 matched controls without immune-mediated diseases were followed from 2014 to 2016 and of these 239 IBD patients and 357 controls developed immune-mediated disease. The overall immune-mediated diseases risk was higher in IBD patients (HR, hazard ratio, 2.47; 95% confidence interval, CI, 2.09-2.91). In a nested case-control study of the IBD cohort, adult patients aged ≥20 years and frequent hospitalisation ≥1 per year were independent risk factors for incident immune-mediated diseases, in contrast, 5-aminosalicylic acid (5-ASA) use had protective effect (odds ratio, 0.61; 95% CI, 0.41-0.90) for developing immune-mediated diseases. In addition, IBD patients with another immune-mediated disease had an increased risk of needing anti-TNF-α agent (HR, 2.40; 95% CI, 2.02-2.84) and developing acute flare (HR, 1.76; 95% CI, 1.37-2.26). Conclusions: The incidence of immune-mediated diseases in IBD patients was higher than that of non-IBD population. 5-ASA use may reduce this risk.