Epidemiology of myasthenia gravis in the province of Ourense (Galicia, Spain)

Abstract

Introduction: Myasthenia gravis (MG) is an autoimmune disease affecting nerve transmission at the level of the neuromuscular junction, and typically causes fluctuating muscle weakness. Epidemiological studies show an increase in MG prevalence, particularly among the older population.

Objective: We performed a retrospective epidemiological study to determine the incidence and prevalence of MG in the province of Ourense (Galicia, Spain), characterised by population ageing.

Material and methods: Patients were selected from our clinical neuromuscular diseases database by searching for patients with an active prescription for pyridostigmine bromide. Incidence was estimated for the period 2009-2018. We calculated prevalence at 31/12/2018. According to census data for the province of Ourense, the population on 1/1/2019 was 307 651, of whom 96 544 (31.4%) were aged ≥ 65 years.

Results: We identified 80 cases of MG, with a prevalence rate of 260 cases/1 000 000 population (95% CI, 202.7-316.4), rising to 517.9/1 000 000 population in those aged ≥ 65 (95% CI, 363.2-672.9). Cumulative incidence in the study period was 15.4 cases per 1 000 000 person-years. Early onset (≤ 50 years) was recorded in 29.1% of cases.

Conclusion: The prevalence of MG in our health district is one of the highest published figures, and the disease is highly prevalent in the older population.

Keywords: Autoimmunity; Autoinmunidad; Incidence; Incidencia; Miastenia gravis; Myasthenia gravis; Prevalence; Prevalencia; Thymoma; Timoma; Vitamin D; Vitamina D.