Myasthenia Gravis (MG) Resource Utilization, Epidemiology, Survival, and Treatment Patterns (MG-REST): Estimating the Clinical and Economic Burden in Ontario, Canada.

OBJECTIVE: The study purpose was to quantify the epidemiology, healthcare resource utilization (HCRU), costs, survival, and treatment patterns of myasthenia gravis (MG) in Canada using population-based administrative data. METHODS: A retrospective cohort study was conducted using administrative data in Ontario, Canada from 2013 to 2020. MG cases were identified using a validated algorithm. Outcomes included MG incidence and prevalence, myasthenic crisis incidence and prevalence, mortality, survival, HCRU, healthcare costs, and treatment patterns (among patients receiving public drug coverage; i.e., individuals ≥ 65 years). RESULTS: The cohort included 2601 individuals with MG (mean age 65.7 years; 46.7% female). Standardized incidence remained stable (3.2-4.0 per 100,000), while prevalence increased from 36 to 42 per 100,000 from 2013/14 to 2019/20. Myasthenic crisis occurred in 8.9% of individuals over the study, with a post-diagnosis incidence rate of 2.6 per 100 person-years and 30-day mortality of 28.1%. 5-year overall survival was 75%, declining to 39% among those with crisis. Mean annual HCRU and direct costs were highest in the first-year post-diagnosis (10.0 specialists visits and CAD $31,693), decreasing in subsequent years. Mean crisis-related costs were CAD $32,948 per person-month in the first 90 days after crisis. During the study among patients ≥ 65 years, most (77.9%) received AChE inhibitors, and excluding AChE inhibitors, corticosteroids were the most common first-line treatment (62.7%). CONCLUSIONS: MG imposes a substantial clinical and economic burden particularly among patients experiencing myasthenic crisis. These findings underscore the need for early intervention and improved access to advanced therapies to mitigate long-term morbidity and healthcare costs.