Incidence and Prevalence of Myasthenia Gravis in Korea: A Population-Based Study Using the National Health Insurance Claims Database

BACKGROUND AND PURPOSE: There have been a few national population-based epidemiological studies of myasthenia gravis (MG) with wide variation of incidence and prevalence rates worldwide. Herein we report the first nationwide population-based epidemiological study of MG in Korea. METHODS: We attempted to estimate the incidence and prevalence rates of MG using the Korean National Health Insurance claims database for 2010 to 2013. Cases with MG were defined as those having claim records with a principal diagnosis of MG and the prescription of acetylcholinesterase inhibitors or immunosuppressive agents including corticosteroids and azathioprine within 2 years after the diagnosis. The year 2010 was set as a washout period, such that patients were defined as incident cases if their first records of MG were observed in 2011. RESULTS: In 2011 there were 1,236 incident cases, and the standardized incidence rate was 2.44 per 100,000 person-years. The standardized prevalence rates were 9.67 and 10.66 per 100,000 persons in 2010 and 2011, respectively. The incidence and prevalence rates peaked in the elderly population aged 60 to 69 years for both sexes. CONCLUSIONS: This is one of the largest national population-based epidemiological studies of MG, and it has confirmed the high incidence and prevalence rates of MG in the elderly population of South Korea.