Citric acid also demonstrated significant protective effects, with inverse variance weighting analysis showing a significant negative correlation with the risk of late-onset myasthenia gravis (OR = 0.001, 95% CI: 2.44 × 10⁻⁶ to 0.21, P = 0.009). The weighted median method (OR = 4.08 × 10⁻⁴, 95% CI: 2.89 × 10⁻⁶ to 0.06, P = 0.015) and MR-Egger regression results were consistent with these findings.