To assess the association between long-term oral corticosteroids (OCS) exposure and overall survival (OS) among patients with myasthenia gravis (MG).

MG is a rare autoimmune neuromuscular disease characterized by muscle weakness and fatigability. OCS are widely used to treat MG; however, the impact of long-term OCS use on OS in patients with MG is unclear.

Data for adult patients with ≥1 primary diagnosis of MG (ICD-10-SE G70.0) provided by neurologist from 01-Jan-2006 to 30-Dec-2020 were extracted from four linkable, longitudinal, nationwide population-based Swedish registries. Patients having ≥1 OCS prescription on or after the MG diagnosis and ≥12-month follow-up period were included. Long-term OCS use was defined as continuous OCS use for ≥3 consecutive months and without gaps of >60 days between prescriptions or end of data availability during the 12 months after MG diagnosis (landmark period); patients not meeting these criteria were defined as short-term users. OS was assessed from the end of landmark period to end of follow-up. OS rates were adjusted for age, gender and other differences in Cox-regression models.

A total of 1,942 patients were included; 272 (22%) were long-term OCS users (mean [SD] age: 65.2 [17.1] years; female, 48.5%); 964 (78%) were short-term OCS users (age, 63.4 [17.0] years; female, 47.4%]). Median OS in long-term OCS users was 10.9 years vs 13.5 years among short-term users (log-rank test: P<0.01). After covariate adjustment, long-term OCS users had a significantly higher risk (42%) of death vs short-term users (adjusted HR: 1.42; 95% CI: 1.10–1.83).