Long Term Mortality in Patients with Myasthenia Gravis: A Nationwide Population-Based Cohort Study in Korea

Objectives: Recent studies have reported conflicting results regarding the mortality risk in patients with myasthenia gravis (MG); however, evidence from East Asian populations remains limited. Understanding the mortality patterns and risk factors of MG is essential for improving patient outcomes. We conducted a nationwide, retrospective cohort study using data from the Korean National Health Insurance Service database to investigate mortality and its associated factors in patients with MG. Methods: Incident MG cases diagnosed between 2005 and 2020 were identified based on validated operational definitions and matched 1:5 with age- and sex-matched controls. All-cause mortality was assessed using Kaplan–Meier analysis, and mortality-associated risk factors were identified by multivariate Cox regression after adjusting for variables. Results: This study included 21,642 patients with MG and 108,210 matched controls. The MG group showed a significantly higher mortality rate than that in controls (144.40 vs. 92.60 per 10,000 person-years; adjusted hazard ratio 1.41, 95% CI 1.34–1.49). Risk factors associated with increased mortality included older age, male sex, high comorbidity burden, high-dose corticosteroid use (≥15 mg/day), thymoma, and myasthenic crisis. Thymectomies were associated with reduced mortality. The leading causes of death included malignancy, cardiac disease, and MG. Myasthenic crisis and thymoma were respectively associated with early mortality and a gradual increase in late mortality. Conclusion: This study demonstrated increased mortality in Korean patients with MG, identifying key disease- and treatment-related risk factors. These findings underscore the need for early risk stratification, comorbidity management, and individualized treatment approaches to improve long-term outcomes.