The Bidirectional Association between Inflammatory Bowel Disease and Atopic Dermatitis: A Systematic Review and Meta-Analysis

<b><i>Background:</i></b> Previous investigations have suggested a significant association between inflammatory bowel disease (IBD) and atopic dermatitis (AD). Yet, outcomes published remain inconsistent. <b><i>Objective:</i></b> To explore the association between IBD and AD by a systematic review and meta-analysis. <b><i>Methods:</i></b> A comprehensive search of studies published from March 1, 1968, to July 26, 2019, was performed in electronic databases as follows: PubMed, Embase, Cochrane Library, and Web of Science. Methodological quality was assessed based on the Newcastle-Ottawa Scale. Data analysis was conducted using R version 3.6.1 (meta package version 4.9-7). <b><i>Results:</i></b> A total of 14 studies were eligible for exploring the association between IBD and AD. Statistically significant differences were found on the risk of AD comorbidity among patients with IBD (risk ratio [RR] 1.83, 95% CI 1.39–2.40), Crohn’s disease (CD; RR 2.06, 95% CI 1.61–2.64), and ulcerative colitis (UC; RR 1.66, 95% CI 1.23–2.24). Compared with non-AD subjects, patients with AD were 48% (<i>p</i> = 0.019), 44% (<i>p</i> = 0.002), and 38% (<i>p</i> = 0.000) more likely to exhibit IBD, CD as well as UC, respectively. <b><i>Discussion:</i></b> Our evidence supported a significant bidirectional association between IBD and AD. Future prospective studies are warranted to explore underlying mechanisms linking them.