Bidirectional Mendelian randomization explores the causal relationship between arthritis and cerebral cortical volume.

Mendelian randomization (MR) method was used to explore the causal relationship between the occurrence of arthritis disease and volume changes in specific cerebral cortical regions. By analyzing the genome-wide association studies summary data, single nucleotide polymorphism data related to arthritis and cerebral cortex volume were selected. Using the inverse variance weighted (IVW) method as the preferred method, MR-Egger, simple mode, weighted median, and weighted mode were used as auxiliary analyses to conduct a 2-sample bidirectional MR analysis. IVW analysis showed that arthritis was positively correlated with the volume of left crus I cerebellum (odds ratio [OR] = 1.18, 95% confidence interval [CI]: 1.09-1.28, P = 9 × 10-5). Gout was negatively correlated with the volume of left frontal operculum cortex (OR = 0.97, 95% CI: 0.95-0.98, P = 5 × 10-5). Gout was positively correlated with left precentral gyrus volume (OR = 1.05, 95% CI: 1.04-1.07, P = 1.9 × 10-11). No positive results were obtained by reverse MR analysis. Arthritis is associated with increased volume of the left crus I cerebellum. Gout is associated with decreased volume of the left frontal operculum cortex. Gout is associated with increased volume of the left precentral gyrus.