Survival Outcomes of Medicare-Covered Elderly US Population With Myasthenia Gravis.

INTRODUCTION/AIM: Survival outcomes have been inadequately studied among people with myasthenia gravis (MG) in the United States (US). We examined the impact of MG and comorbid conditions on longevity.

METHODS

We performed a longitudinal study using Medicare claims data (2006-2019). Incident MG cohort was identified based on the following criteria: age ≥ 65 years; ≥ 1 month of fee-for-service Parts A and B coverage; no health maintenance organization coverage; initial and subsequent MG claims within 2010-2011 separated by ≥ 28 days. A non-MG cohort of five times the number of the MG group was selected, matching for age, sex, region, and Medicare coverage duration. Overall and cause-specific mortality were compared between cohorts in the subsequent 8-10 Years using Kaplan-Meier plots and Cox proportional hazard models, adjusted for the Charlson Comorbidity Index (CCI).

RESULTS

Cohorts of 6024 incident MG and 30,083 control beneficiaries were Included. The mortality rate was higher in the MG cohort compared to controls (66.8 vs. 57.1 per 1000-person-year, p < 0.0001). After adjusting for time-varying CCI, no significant difference in survival was observed between two cohorts (adjusted hazard ratio 1.09 [0.87-1.36], p = 0.47). Sixteen percent of deaths in the MG cohort were attributed to MG. Compared to the non-MG cohort, mortality rates (per 1000-person-year) specific to infections were higher among the MG cohort (2.0 vs. 1.2) while malignancies and dementia-specific mortality rates were lower (10.3 vs. 12.5 and 4.7 vs. 7.2), all p < 0.01.

DISCUSSION: Long-term mortality is increased in elderly MG patients compared to non-MG counterparts, driven by their higher comorbidity burden.