Epidemiology, Patient Characteristics, and Treatment Patterns of Myasthenia Gravis in Taiwan: A Population-Based Study

Abstract

Introduction: Myasthenia gravis (MG) is a chronic neuromuscular disease leading to significant disease burden. This study aimed to investigate the epidemiology of MG in Taiwan.

Methods: A retrospective study was conducted using the Taiwan National Health Insurance Research Database. Prevalent patients with MG diagnosis (either ocular or generalized MG) from 2013 to 2019 were identified, and 2813 patients with initial MG diagnosis from 2014 to 2019 were further defined as the incident cohort. Patient characteristics, treatment patterns, and the occurrence of MG-related events were analyzed.

Results: The number of prevalent patients with MG increased from 4476 in 2013 to 5752 in 2019, with the prevalence rate increasing from 19 to 24 per 100,000 population. The incidence rate also slightly increased from 1.9 to 2.3 per 100,000 population during the study period. Almost all incident patients (99%, n = 2791) received MG-related treatment during the follow-up period. Among 1876 patients who received monotherapy as their initial treatment in the outpatient setting, the mean time from the index date to initial treatment was 48.8 (standard deviation 164.3) days, and most patients received acetylcholinesterase inhibitors (88.5%, n = 1661) as their initial treatment. During the first year after the index date, 133 (4.7%) incident patients experienced their first myasthenic crisis, and 96.2% of these events occurred within 3 months.

Conclusion: The prevalence of MG increased steadily in Taiwan, and the treatment of patients with MG was consistent with guidelines. Despite a high treatment rate, patients still experienced MG-related events, highlighting the limitation of current treatments and emphasizing the need for early intervention and novel treatment approaches.

Keywords: Disease burden; Epidemiology; Myasthenia gravis (MG); Myasthenic crisis; Treatment pattern.

Fig. 1

a Prevalent patients with MG in Taiwan increased steadily from 2013 to 2019 and the percentage of patients receiving PP/PE remained consistent over the study period. b Incident patients with MG and the incidence rate of MG in Taiwan from 2014 to 2019. There were 440 to 540 newly diagnosed patients with MG annually. MG myasthenia gravis, PP/PE plasmapheresis or plasma exchange

Fig. 2

Treatment patterns among incident patients with MG who received initial treatment in an outpatient setting. Most patients received AChE inhibitors as their initial treatment and 81.6% patients had their treatment changed during the follow-up period. The median time from initial treatment to regimen change was 58 days. ¹Data of IST + AChE inhibitors + oral corticosteroids and IST were combined in accordance with the masking rule of the NHIRD. ²Second regimen was not reported in accordance with the masking rule of the NHIRD. AChE acetylcholinesterase, NSIST non-steroidal immunosuppressants, NR not reported, SD standard deviation

Fig. 3

Occurrence of a PP/PE and b MG crisis in the first year after the initial MG diagnosis and the distribution of time from the index date to the first a PP/PE or b MG crisis. Of the patients who experienced PP/PE or MG crisis in the first year of the initial MG diagnosis, more than two-thirds of them experienced these events at the time of diagnosis. ¹Data of PP/PE between 0–3 months and 3–12 months were combined in accordance with the masking rule of the NHIRD. MG myasthenia gravis, PP/PE plasmapheresis or plasma exchange

Fig. 4

Cumulative event of a PP/PE and b MG crisis among incident patients with MG without the event at the index date. With the longest follow-up of 96 months, the median time to the first PP/PE was 3.4 months, and for MG crisis it was 3.7 months. MG myasthenia gravis, PP/PE plasmapheresis or plasma exchange