3.2 Instrumental Variable Selection Results
Using the inverse variance weighting method, MR-Egger regression, and weighted median method, we evaluated the causal relationship between four fitness supplements and their related metabolites and the risk of myasthenia gravis. The inverse variance weighting analysis showed a significant negative association between genetically predicted glutamine levels and late-onset myasthenia gravis risk (OR = 0.64, 95% CI: 0.46 to 0.87, P = 0.005), indicating that each standard deviation increase in glutamine levels is associated with a 36% reduction in the risk of late-onset myasthenia gravis. The weighted median method (OR = 0.63, 95% CI: 0.42 to 0.94, P = 0.024) and MR-Egger regression yielded effect estimates consistent in direction.