Supplementary Material for: 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.

<b><i>Background:</i></b> 既往研究提示炎症性肠病（inflammatory bowel disease, IBD）与特应性皮炎（atopic dermatitis, AD）之间存在显著关联，但已发表的研究结论仍存在不一致性。<b><i>Objective:</i></b> 本研究旨在通过系统评价（systematic review）与荟萃分析（meta-analysis）探讨炎症性肠病与特应性皮炎之间的关联。<b><i>Methods:</i></b> 于1968年3月1日至2019年7月26日期间，在PubMed、Embase、Cochrane Library及Web of Science四大电子数据库中全面检索相关研究。采用纽卡斯尔-渥太华量表（Newcastle-Ottawa Scale）评估研究的方法学质量。数据分析依托R 3.6.1版本（meta包版本4.9-7）完成。<b><i>Results:</i></b> 最终纳入14项符合纳入标准的研究以分析炎症性肠病与特应性皮炎的关联。结果显示，炎症性肠病患者发生特应性皮炎合并症的风险存在统计学显著性差异（风险比[risk ratio, RR] 1.83，95%置信区间[95% confidence interval, CI] 1.39~2.40）；其中克罗恩病（Crohn’s disease, CD）患者的对应风险比为2.06（95%CI 1.61~2.64），溃疡性结肠炎（ulcerative colitis, UC）患者则为1.66（95%CI 1.23~2.24）。与非特应性皮炎受试者相比，特应性皮炎患者罹患炎症性肠病、克罗恩病及溃疡性结肠炎的风险分别升高48%（<i>p</i>=0.019）、44%（<i>p</i>=0.002）及38%（<i>p</i>=0.000）。<b><i>Discussion:</i></b> 本研究证据证实炎症性肠病与特应性皮炎之间存在显著的双向关联。未来仍需开展前瞻性研究以阐明二者关联的潜在机制。