Comorbidities and Treatment Patterns in People With Myasthenia Gravis in Denmark, Finland and Sweden: A Population-Based Observational Study

Introduction/Aims: Comorbidities are frequent in myasthenia gravis (MG) and may affect treatment choices. Conversely, MG treatments may impact the risk of comorbidity. Our objective was to examine comorbidity and MG treatment patterns in nationwide MG cohorts in Denmark, Finland, and Sweden. Methods: We included individuals with ≥ 2 MG diagnoses (ICD codes) in nationwide health registries between 2000 and 2020 and analyzed comorbidities before and after MG diagnosis and MG-related treatments during follow-up. Results: Among 8819 people with MG (pwMG), 3159 were incident cases with data available ±5 years from diagnosis. Circulatory diseases were the most frequent comorbidity (19%–29%) before diagnosis, mostly explained by hypertension (13%–24%). After diagnosis, anemia and osteoporosis prevalence increased three to six fold. Mental health disorders were more frequent in younger (0–64 years) than older (≥ 65 years) pwMG. In the first year after diagnosis, acetylcholinesterase inhibitors (AChEIs) were the most used treatment in Finland (41%) and Sweden (34%), and corticosteroids (CSs) with nonsteroidal-immunosuppressive therapy (NS-IST) in Denmark (33%). By year 5, the proportion of pwMG receiving NS-IST, CS, or their combination was similar in the three countries (Denmark 47%, Finland 40%, and Sweden 41%). Only 5%–7% remained treatment-naive throughout follow-up. Discussion: MG treatment was broadly similar across the three Nordic countries, while also reflecting nation-specific therapeutic guidelines. Many pwMG required multiple therapies, underscoring risks of long-term immunosuppression and highlighting the need for vigilant management and future research of safer strategies.