Unexpected longevity in myasthenia gravis: a multi-state population-based comparison with multiple sclerosis and the U.S. population.

BACKGROUND: This study compares age at death in patients with myasthenia gravis (MG) and multiple sclerosis (MS) with the general U.S. population and examines age at death patterns during a period preceding modern high-efficacy therapies.
OBJECTIVE: To compare age at death among individuals with MG and MS with the general population and assess differences in age at death between MG and MS.
DESIGN: Retrospective population-based study using death certificate data from four U.S. states (Florida, Wisconsin, Texas, and New York) for 2000, 2005, 2010, and 2015.
METHODS: Individuals with MG or MS listed on death certificates were identified. Age at death was compared between MG and MS among four states and contemporaneously with U.S. population via Social Security life tables, adjusting for sex and geography. Because data were provided in different formats across states (individual-level, aggregated, and categorical), analyses were tailored to each dataset while addressing the same underlying question. During the study period, high-efficacy targeted therapies for both conditions were not yet available, allowing comparison of mortality patterns under standard-of-care treatment.
RESULTS: Age at death of MS patients was significantly lower than the general population (-12.4 years, p < 0.001). In contrast, MG patients showed a higher mean age at time of death compared with the general population (+4.8 years, p < 0.0001) and died significantly later than MS patients (+15.5 years, p < 0.001, adjusted for sex and year). These patterns were consistent across datasets. Despite a higher reported burden of age-related comorbidities in MG populations, MG patients demonstrated higher mean age at death than both MS patients and the general population.
CONCLUSION: MG was associated with significantly older age at death compared with both MS and the general population under historical standard-of-care conditions. These findings suggest that survival patterns in MG differ from those in MS and raise questions about the factors driving this difference. Further studies are needed to clarify the roles of disease biology, comorbidity, age at diagnosis, and healthcare utilization in shaping long-term outcomes.