Nationwide population-based epidemiological study of myasthenia gravis in taiwan

The purpose of this study is to investigate the epidemiology and medical expenses of myasthenia gravis (MG) in Taiwan.

Cases of MG were identified from the National Health Insurance Research Database with corresponding codes of the International Classification of Diseases, ninth revision (ICD-9), from January 2000 to December 2007. Age- and sex-specific incidences were estimated by dividing the incidence number by population data obtained from the Department of Statistics, Ministry of the Interior.

During the study period, 5,211 cases were identified. The incidence ratio of males to females was 0.68. The average annual incidence rate was 2.1/100,000. MG occurred in all age groups with a higher incidence in older individuals and the lowest incidence in the 10- to 14-year-olds for both sexes. Among the 5,211 cases, 615 (12%) had a neoplasm of the thymus. The prevalence increased steadily during the study period from 8.4/100,000 in 2000 to 14.0/ 100,000 in 2007.

This is the first population-based epidemiological study of MG in Taiwan. The incidence rate and prevalence were higher than in most published studies, especially in old age groups.