Prevalence of myasthenia gravis in the Catalan county of Osona

Abstract

Introduction: The reported prevalence of myasthenia gravis ranges between 5 and 24 cases per 100,000, and people over 65years account for less than 50% of all cases. The prevalence and clinical characteristics of myasthenia gravis in the county of Osona were studied in patients younger and older than 65.

Methods: The study draws from the county-based prospective myasthenia gravis register implemented by the Neurology Department at Hospital General de Vic in 1991.

Results: The prevalence of myasthenia gravis was 32.89×10⁵ inhabitants (95%CI, 23.86-41.91). The standardized prevalence (European population) was 35.47×10⁵ inhabitants (95%CI, 26.10-44.84). The ratio of women to men was 1.3. Overall, the group of patients older than 65 accounted for 62.75% of all cases. The prevalence of myasthenia gravis increased considerably in older age groups. No cases were registered among patients under 25years old, prevalence was 21.87×10⁵ in the 25 to 64 age group, and prevalence in patients over 65 years increased to 122.35×10⁵. The clinical characteristics prior to treatment and at the cut-off date are similar (P>.05) in patients younger than 65 and those aged 65 and older.

Conclusions: These figures show the highest prevalence rate reported to date. This high prevalence is due to the rate observed among patients older than 65. These results provide a new warning that myasthenia gravis may be underdiagnosed in the elderly population.

Keywords: Ageing; Edad avanzada; Geriatric neurology; Immunosenescence; Miastenia gravis; Myasthenia gravis; Neuroepidemiology; Neuroepidemiología; Neurogeriatría; Prevalence; Prevalencia; Senescencia inmunológica.