Myasthenia gravis: a higher than expected incidence in the elderly.

This 10-year (1991 to 2000) prospective study of MG in the county of Osona (Barcelona, Spain) reveals an annual incidence rate of 21.27 cases per million inhabitants (95% CI 13.89 to 31.16). Incidence increased from 5.03 x 10(6) in the age group of 0 to 14 years to 14.68 x 10(6) in the age group of 15 to 64 years and to 63.38 x 10(6) in the older population. These results, the highest reported to date, may be explained by the population aging.