Bidirectional relationship between atopic dermatitis and inflammatory bowel disease: A systematic review and meta-analysis

Background Recently, atopic dermatitis has been suggested as a systemic inflammatory disorder that can accompany other inflammatory diseases, including inflammatory bowel disease. However, comprehensive reviews that specifically focus on the association between inflammatory bowel disease and atopic dermatitis are lacking. Objective To determine the association between inflammatory bowel disease and atopic dermatitis. Methods We searched for relevant studies from MEDLINE, EMBASE, and the Cochrane Library from inception to November 22, 2019. Considering a potential bidirectional relationship, studies reporting inflammatory bowel disease in patients with atopic dermatitis and atopic dermatitis in patients with inflammatory bowel disease were evaluated separately. Results We included 10 studies with 95,291,110 patients (4 studies on the prevalence of atopic dermatitis in inflammatory bowel disease, 2 on the prevalence and incidence of inflammatory bowel disease in atopic dermatitis, and 4 on either the prevalence or incidence of inflammatory bowel disease in atopic dermatitis). Meta-analyses revealed a statistically significant association between inflammatory bowel disease and atopic dermatitis in both directions (4 studies on atopic dermatitis prevalence in inflammatory bowel disease, odds ratio 1.39, 95% confidence interval 1.28-1.50; 5 on inflammatory bowel disease prevalence in atopic dermatitis, odds ratio 1.35, 95% confidence interval 1.05-1.73; and 3 studies on inflammatory bowel disease incidence in atopic dermatitis, relative risk 1.46, 95% confidence interval 0.98-2.17). Limitations A small number of observational studies were reviewed. Conclusion Published literature suggests a bidirectional relationship between inflammatory bowel disease and atopic dermatitis.