OBJECTIVES: Myasthenia gravis (MG) is a chronic autoimmune disease marked by heterogeneous presentations of progressive muscle weakness with a typical age of onset between 20-40 years. Treatment advancements have increased the lifespan of people with MG, but disease burden in older populations is not well-characterized. The objective of this analysis was to characterize the burden of MG among elderly Medicare beneficiaries in terms of the prevalence and association between muscle weakness and psychiatric health.

METHODS: A retrospective analysis was conducted using Medicare claims (Q1 2019-Q3 2022 for patients with MG. Analysis eligible patients were identified via ICD-10-CM diagnosis codes for MG and were required to have >12 months of continuous Part A/B coverage; patients <65 were excluded. Prevalence of constitutional symptoms for malaise and fatigue/weakness (‘malaise/fatigue’) and mental health conditions for mood and major depressive disorders (‘mood/major depression’) was similarly determined. Likelihood of mood/major depression in the presence of malaise/fatigue was assessed via Wald test using R Statistical Software v4.2.2.

RESULTS: 1,861 MG patients were eligible for analysis. Mean age was 77.9 years, 44.7% were female, and 91.1, 4.5, and 4.4% were White, Black, and Other race/ethnicity, respectively. Prevalence of malaise/fatigue and mood/major depression were 51.9 and 27.3%, respectively. Malaise/fatigue was associated with a greater odds of comorbid mood/major depression (OR 2.35, 95% CI: 1.90-2.91; p<0.0001).

CONCLUSIONS: In this analysis the prevalence of malaise/fatigue and mood/major depression was common in Medicare-aged MG patients. That patients with malaise/fatigue were more than twice as likely to have comorbid mood/major depression demonstrates a significant association between physical mobility and psychiatric health. Adjusted longitudinal studies are needed to investigate a potential causal link. Despite this evidence gap, the burden of MG among older patients is substantial and represents an unmet need that does not appear to be addressed by current treatments.