Internal Medicine
Online ISSN : 1349-7235
Print ISSN : 0918-2918
ISSN-L : 0918-2918
ORIGINAL ARTICLES
Increase in Incidence of Elderly-onset Patients with Myasthenia Gravis in Nagano Prefecture, Japan
Masayuki MATSUDANaoko DOHI-IIJIMAAkinori NAKAMURAYoshiki SEKIJIMAHiroshi MORITAShigeyuki MATSUZAWAShun-ichi SATOHiroyuki YAHIKOZAWAKen-ichi TABATASohei YANAGAWAShu-ichi IKEDA
Author information
JOURNALS OPEN ACCESS

2005 Volume 44 Issue 6 Pages 572-577

Details
Abstract

Objectives In European countries and the United States the incidence of elderly-onset myasthenia gravis (MG) has recently been increasing. To investigate whether the incidence of the elderly-onset MG has increased in Nagano Prefecture of Japan, we divided the patients into young and elderly groups, and retrospectively examined their incidence.
Patients and Methods On the basis of two-step questionnaires sent to hospitals and the patient list of the intractable disease registration system in Nagano Prefecture we studied 213 MG patients diagnosed between 1982 and 2001. This 20-year period was divided into 4 five-year terms, and the incidence of MG in young- (younger than 65) and elderly-onset (65 or older) groups was investigated separately for each term.
Results The ratio of the elderly-onset group showed a significantly positive correlation with terms irrespective of associated thymoma (r=0.98, p<0.05). There was a significant difference in the mean onset age among the 4 terms (p<0.005). The standardized incidence of MG gradually increased in both young- and elderly-onset groups as well as in the whole age range. The elderly group showed a particularly high incidence in females (12.01/million/year) and in patients without thymoma (8.78/million/year) in the final five years.
Conclusions We confirmed that the incidence of elderly-onset MG has recently been increasing in the Nagano Prefecture. Since the change of the age distribution in this district is almost identical to that of the whole country, the incidence of MG might have been increasing in Japan as a whole, particularly in the elderly population.

Information related to the author
© 2005 by The Japanese Society of Internal Medicine
Previous article Next article
feedback
Top