Association Between Statin Initiation and Myasthenia Gravis Crisis

Statins are widely prescribed for preventing cardiovascular disease, but concerns remain that they may trigger or exacerbate myasthenia gravis (MG). We evaluated whether statin initiation increases the risk of an MG crisis using a self-controlled case series (SCCS) design.

This SCCS study analyzed nationwide Korean claims data from 2007 to 2023. We included patients in whom statin therapy was initiated after an MG diagnosis and who experienced at least one MG crisis during a 730-day period spanning from 365 days before to 365 days after statin initiation. The primary outcome was an MG crisis during a 365 days follow-up. Incidence rate ratios (IRRs) with 95% confidence intervals (CIs) were estimated using conditional Poisson regression models.

Among 16,268 patients with MG in the claims database, 45 patients meeting the study inclusion criteria were included in the SCCS analysis. The risk of an MG crisis was higher during the first 30 days following statin initiation (IRR=3.60, 95% CI=1.50-8.64), but not during later periods (31-90 days: IRR=1.00, 95% CI=0.34-2.95; 91-180 days: IRR=0.87, 95% CI=0.34-2.23; 181-365 days: IRR=0.73, 95% CI=0.32-1.67). Subgroup analyses showed that the risk was higher in patients aged ≥65 years (IRR=10.31, 95% CI=2.59-41.05) and females (IRR=3.71, 95% CI=1.18-11.66). The findings were consistent across the sensitivity analyses.

Statin initiation was associated with an increased risk of an MG crisis during the early postinitiation period, with no evidence of an elevated risk during longer-term use. Close monitoring is recommended during the early phase of statin therapy in patients with MG, particularly in the elderly, females, and users of lipophilic statins or concomitant beta blockers.