Causal relationship between atopic dermatitis and infectious gastroenteritis: a bidirectional mendelian randomization study

[Objective] To investigate the causal relationship between atopic dermatitis (AD) and infectious gastroenteritis using bidirectional two-sample Mendelian randomization (MR), and to assess the risk of infectious gastroenteritis in patients with AD. [Methods] Based on pooled data from genome-wide association studies, single nucleotide polymorphisms (SNPs), which were independent of each other and strongly associated with both atopic dermatitis (AD) and infectious gastroenteritis, were selected as instrumental variables. MR analysis was performed using inverse variance weighted (IVW), MR Egger's method, weighted median, weighted mode, and simple mode. The Cochran Q test for heterogeneity, the Mendelian randomization pleiotropy residual sum and outlier test, the MR Egger intercept test for multivariate analysis, and the “leave-one-out” method were used for sensitivity analysis. Odds ratio and 95%CI were used as effect indicators to investigate the bidirectional causal relationship between AD and infectious gastroenteritis. [Results] IVW analysis showed that AD increased the risk of infectious gastroenteritis (OR=1.030, 95%CI:1.006~1.056, P=0.015). The results were further confirmed by the weighted median method. However, no evidence suggested that infectious gastroenteritis increased the risk of AD in IVW analysis (OR=1.111, 95%CI:0.910~1.357, P=0.299), simple model, weighted model, weighted median and MR Egger analyses. [Conclusions] This study shows a significant causal effect of AD on the risk of infectious gastroenteritis, but no evidence supports a reverse causal relationship.