Identification of High-Risk Population for Mortality and Severe Clinical Outcomes Among Patients With Myasthenia Gravis: A Nationwide Population-Based Cohort Study in Korea.

Background: Myasthenia gravis (MG) is a rare chronic neurological condition characterized by skeletal muscle weakness and fatigue. Some patients with MG have poorly controlled symptoms with conventional treatments. While new treatments could be considered in patients with poorly controlled MG, their costs are considerably higher and may impose a financial burden on patients and the national health insurance system. Therefore, we sought to identify high-risk populations for mortality and severe clinical outcomes among MG patients to effectively allocate health resources.

Methods: A population-based cohort study was conducted using the Health Insurance Review and Assessment database from South Korea (2007-2023). Among patients with incident MG, we defined six clinical criteria expected to be associated with poor prognosis of MG. Separate study cohorts were constructed for the history of each criterion within two years of the first MG diagnosis to compare the risk of mortality, myasthenic crisis (MC), intensive care unit (ICU) admission, and MG-related hospitalization between patients. To adjust for any potential confounding, each covariate was assessed for inclusion in a multivariate Cox proportional hazards model, and findings were presented using hazard ratios (HRs) and 95% confidence intervals (CIs).

Results: We identified 10,458 patients with incident MG (54.2% aged over 60 years; 56.8% female), of whom 361 and 319 were defined as MG patients with history of MC and refractory MG, respectively. Among MG patients, patients with history of any of the predefined clinical criteria showed worse prognosis than those without. Patients with a history of MC had a significantly higher risk of mortality compared to those without (54.0 vs. 17.9 per 1,000 person-year; HR, 2.33; 95% CI, 1.87-2.89). Similarly, across six different criteria, including refractory MG, the risk of serious clinical outcomes, defined MC, ICU admission, and MG-related hospitalization were increased in patients who met the criteria versus those who didn't.

Conclusion: Our study identified high-risk populations among patients with MG. Patients with a history of certain clinical criteria, including MC or refractory MG, had elevated risk of mortality and severe clinical outcomes. These findings may be utilized to establish the reimbursement strategy by identifying MG patients with a priority need for new treatments.