Prevalence, Incidence of Myasthenia Gravis in Older US Population Is Increasing

Between 2006 and 2019, increasing trends in myasthenia gravis prevalence and incidence among the elderly US population were observed, according to study findings published in Neurology.

Using Medicare claims data from 2006 to 2019, researchers conducted a retrospective longitudinal study to estimate myasthenia gravis prevalence, incidence, and mortality among Medicare Fee-For-Service (FFS) beneficiaries aged 65 and older who had at least 1 month of FFS Part A/B coverage.

Participants were grouped into 2-year periods from 2006 to 2007 through 2018 to 2019. Myasthenia gravis cases were defined as at least 2 outpatient myasthenia gravis-related claims within the 2-year period that were separated by at least 28 days, or an inpatient and outpatient claim separated by 28 days within the 2-year period. Poisson regression was used to examine trends of prevalence, incidence, and mortality rates over time.

A total of 85,011 beneficiaries were identified for inclusion between 2006 and 2019.

Over the course of the 14-year study period, the prevalence or myasthenia gravis increased from 81.1 to 118.6 cases per 100,000 beneficiaries (P <.001). This trend was consistent across all sex, age, race and ethnicity, and census region subgroups. The highest prevalence rates were observed among participants who identified as non-Hispanic White (129.6 per 100,000 person-years in 2018-2019) and those aged 80 and older (158.4 per 100,000 person-years in 2018-2019).

Myasthenia gravis incidence increased from 12.2 to 13.3 cases per 100,000 person-years between 2008 to 2009 and 2018 to 2019 (P <.001). Increasing incidence trends were significant in the following subgroups: men and women, all age groups aside from the aged 75 to 79 group, non-Hispanic White race and ethnicity, and the Northeast, Midwest, and South regions.

All-cause mortality was stable over the 14-year study period, decreasing from 6.26 deaths per 100 person-years in 2006 to 2007 to 5.67 deaths per 100 person-years in 2018 to 2019. This decrease in mortality was most pronounced in the aged 75 to 79 subgroup (trend of change, -2.9% per 2-year period; 95% CI, -4.6% to -1.3%; P <.001).

Study limitations include potential systematic biases and the exclusion of individuals aged younger than 65.

“The increased MG [myasthenia gravis] incidence and prevalence rates over the 14-year span could indicate an increased disease burden,” the researchers concluded.

Disclosure: This research was supported by Argenx BVBA. Multiple study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.