Patients with Atopic Dermatitis Are More Susceptible to Developing Inflammatory Bowel Disease

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Data from longitudinal studies showed that atopic dermatitis (AD) may increase the risk of developing inflammatory bowel disease (IBD).¹ Additionally, patients with AD have a high risk of being diagnosed with IBD subtypes such as Crohn’s disease and ulcerative colitis.

The review analyzed only cohort and case-control studies, which differs from previous systemic reviews on the 2 conditions. According to investigators, this study design was chosen “because of its unique advantages in causal inference.” PubMed, CENTRAL, Embase, Scopus, Web of Science, and Google Scholar were used to identify the literature. The research included studies published up to April 15, 2024, with no limit on the initial publication date. Furthermore, only studies that reported multivariate-adjusted associations were utilized.

Investigators used a combination of search terms that included AD, eczema, or atopy and ulcerative colitis, Crohn’s disease, or IBD, to identify relevant articles. They collected study characteristics, demographic details of the sample size, proportion of each disease, and follow-up, to establish which were eligible. Follow-up periods ranged from 4 to 19 years. The Newcastle-Ottawa scale was used to evaluate study quality. Each study was awarded either 7 or 8 points on this scale.

The initial search yielded 1778 article results but after exclusion and screening processes, 8 retrospective studies were included. It included a total of 61,190,816 participants, all among the general population of adults and children.

In terms of developing IBD, the risk was significantly increased (OR: 1.37, 95% CI: 1.31–1.43) and can range from 31% to 43% in patients with AD. It was also a high-risk factor for Crohn’s disease (OR: 1.51, 95% CI: 1.31–1.76) and ulcerative colitis (OR: 1.33, 95% CI: 1.13–1.56). This correlates to a 51% risk increase in Crohn’s disease and a 33% risk increase in ulcerative colitis.

In terms of sensitivity analysis, the odds ratio for IBD ranged from 1.34 to 1.44. This varied from 1.46 to 1.58 in Crohn’s disease and 1.24 to 1.37 in ulcerative colitis, showing that the results were not influenced by a singular study.

There were also some significant correlations among subgroups, such as the presence of asthma and other allergies. Particularly in the pediatric subset, it was observed that AD increased the risk of Crohn’s disease. However, there was no significant association between AD and ulcerative colitis in pediatric patients.

In terms of limitations, some possible errors in registry data made it unable to categorize results by age, gender, and disease severity. These factors could play a very important role in the correlation between AD and IBD and should be evaluated in future research.

About 0.3% of the world population suffers from IBD.² Although it is known that both AD and IBD share several genetic, environmental, and microbial risk factors, this literature is the first of its kind and differs from past reviews.

“In contrast, the present study incorporated high-quality longitudinal cohort studies, effectively addressing the limitations of unclear time series present in earlier research and enhancing the ability to infer causality.” the authors wrote. “A second important differentiating factor of this review is the use of only multivariate-adjusted data. When examining a casual association of exposure and outcome, the importance of deliberate and rigorous control of confounders cannot be underestimated.”

It is recommended that patients with AD should be closely monitored for bowel symptoms and provided with timely therapeutic interventions due to the future risk of IBD. Further research can distinguish treatment options and reduce the burden of IBD in patients with AD.

References

1. Yu P, Lin L, Xue, K, et al. The Association Between Atopic Dermatitis and Inflammatory Bowel Disease Risk: A Meta-Analysis of Longitudinal Studies, JGH Open, https://doi.org/10.1002/jgh3.70077

2. Ng SC, Shi HY, Hamidi N, et al. Worldwide incidence and prevalence of inflammatory bowel disease in the 21st century: a systematic review of population-based studies [published correction appears in Lancet. 2020 Oct 3;396(10256):e56. doi: 10.1016/S0140-6736(20)32028-6]. Lancet. 2017;390(10114):2769-2778. doi:10.1016/S0140-6736(17)32448-0