Atopic dermatitis and rheumatoid arthritis: a bidirectional Mendelian randomization study

Background: The association between atopic dermatitis(AD) and rheumatoid arthritis (RA) has been reported. However, causality has not yet been established. In the present study, Mendelian randomization (MR) analyzes were used to assess whether atopic dermatitis and rheumatoid arthritis are causally associated. Objective: In the present study, MR analyzes were used to evaluate whether atopic dermatitis and rheumatoid arthritis are causally associated. Methods: We extracted summary-level data for atopic dermatitis and rheumatoid arthritis. Inverse variance-weighted (IVW) analysis was used as the primary analysis. Alternate methods, including weighted median, MR Egger, MR pleiotropy residual sum and outlier, weighted mode, and leave-one-out analysis, were performed to assess pleiotropy. Results: No evidence of an effect of rheumatoid arthritis on the risk of atopic dermatitis was found in inverse-variance weighted (OR = 1.043，95% CI =0.959-1.134，p = 0.328). No evidence of an effect of atopic dermatitis on the risk of rheumatoid arthritis was also found (OR=1.026,95% CI =0.903-1.166, p = 0.691). Conclusions: The large MR analysis indicated that there is no causal relationship between rheumatoid arthritis and atopic dermatitis.