Causal relationship between rheumatoid arthritis and carpal tunnel syndrome: a bidirectional two-sample Mendelian randomization study.

Background: Although there is considerable evidence of a robust correlation between rheumatoid arthritis (RA) and carpal tunnel syndrome (CTS) in previous research, the causal link between the two remains a topic of controversy.

Methods: We conducted a two-sample Mendelian randomization (MR) study to explore the causal impact of RA on CTS. We obtained aggregate data from genome-wide association studies (GWAS) of CTS (ebi database and GEO database) and RA (FinnGen database). This study employed five MR analysis methods, with a focus on the inverse variance-weighted (IVW) method. Sensitivity analyses were conducted to ensure the robustness of the results of this study. Additionally, we performed reverse MR analysis.

Results: We selected 84 and 78 single nucleotide polymorphisms (SNPs) significantly associated with RA from two databases as instrumental variables (IVs), respectively. Our results showed that RA patients have a higher risk of getting CTS regardless of whether the ebi database (IVW, OR = 1.045, 95% CI: 1.016-1.075, P = 0.002) or the GEO database (IVW, OR = 1.001, 95% CI: 1.001-1.002, P = 0.001) is selected for CTS data. However, the MR analysis showed no causal link between CTS and the increased risk of RA (ebi: IVW, OR = 1.084, 95% CI: 0.918-1.279, P = 0.341; GEO: IVW, OR = 1.968, 95% CI: 0.011-360.791, P = 0.799).

Conclusion: The analysis revealed that RA can increase the risk of CTS, but did not support the causal relationship that CTS can increase the risk of RA.