Atopic Diseases Are Associated With Development of Inflammatory Bowel Diseases in Korea: A Nationwide Population-based Study

Background & aims: The association between atopic diseases and inflammatory bowel diseases (IBD) is unclear. We conducted a nationwide population-based study in Korea to investigate the effect of atopic diseases on the development of IBD. Methods: A total of 9,923,521 participants, who received a medical check-up in 2009, were included and followed through 2017. The presence of any atopic diseases, including atopic dermatitis (AD), allergic rhinitis (AR), and asthma, was evaluated. Patients who developed IBD, including Crohn's disease (CD) and ulcerative colitis (UC), were identified using claims data from National Health Insurance; the association between atopic diseases and the risk of IBD was evaluated using Cox proportional hazard models, and presented as adjusted hazard ratios (aHRs) with 95% CIs. Results: During a mean follow-up period of 7.3 years, 1419 patients (0.014%) developed CD and 5897 patients (0.059%) developed UC. The incidences of CD (per 100,000 person-years) were 3.756, 2.248, and 2.346 in patients with AD, AR, or asthma, respectively. The incidences of UC were 11.952, 9.818, and 9.358 in patients with AD, AR, or asthma, respectively. Multivariable analysis revealed that the aHRs for incident CD in patients with AD, AR, or asthma were 2.02, 1.33, and 1.60 (95% CIs, 1.118-3.663, 1.149-1.529, and 1.193-2.136, respectively) compared with controls. The risks of incident UC in patients with AD, AR, or asthma were 1.51, 1.32, and 1.29 (95% CIs, 1.082-2.104, 1.229-1.410, and 1.115-1.491, respectively) compared with controls. Moreover, an increase in the number of atopic diseases gradually increased the risk for CD and UC; for 1 or 2 or more atopic diseases, the aHRs for CD were 1.35 and 1.65 (95% CIs, 1.171-1.560 and 1.146-2.376), and the aHRs for UC were 1.30 and 1.49 (95% CIs, 1.211-1.392 and 1.249-1.774), respectively. Conclusions: Based on a nationwide population-based study in Korea, patients with any atopic disease, including AD, AR, or asthma, have an increased risk for CD and UC. The risk for IBD increases with the increase in the number of atopic diseases.restrictio