The Association Between Atopic Dermatitis and Inflammatory Bowel Disease Risk: A Meta-Analysis of Longitudinal Studies

Aims: This review aimed to investigate whether atopic dermatitis (AD) increases the risk of inflammatory bowel disease (IBD) by analyzing data from longitudinal studies. Methods: Cohort and case–control studies evaluating the association between AD and the risk of IBD, Crohn's disease (CD), or ulcerative colitis (UC) were included. Literature searches were conducted in PubMed, CENTRAL, Embase, Scopus, and Web of Science databases up to April 15, 2024. Results: A total of eight retrospective cohort studies comprising 61 190 816 participants were included. Meta-analysis revealed that AD significantly increased the risk of IBD (OR: 1.37, 95% CI: 1.31–1.43) without statistical heterogeneity. Further pooled analysis showed that AD was a significant risk factor for CD (OR: 1.51, 95% CI: 1.31–1.76) and UC (OR: 1.33, 95% CI: 1.13–1.56), with high inter-study heterogeneity (I² = 83% and 89%, respectively). Sensitivity analyses confirmed the robustness of the results. Conclusion: AD is associated with an increased risk of IBD, significantly elevating the risk of both CD and UC.