A population based epidemiological study on myasthenia gravis in Estonia

Objective: To describe the occurrence of myasthenia gravis in the Baltic area. Methods: Data were obtained from hospital files recorded during the period 1942 to 1996 from neurologists and the patient organisation. Survival data were checked with the Estonian Citizenship and Migration Board. Prevalence was determined on 1 January 1997. A questionnaire on the course of myasthenia gravis was sent to all the prevalent patients. Results: The size of the population surveyed was 1462130. The average annual incidence from 1970 to 1996 was 4.0 per million (women, 5.2; men, 2.6). The point prevalence was 99 per million (women, 133; men 59). The incidence in the younger age group (<50 years) was 3.4 per million (women, 4.8; men, 1.9) and in the older age group(≥50 years), 5.5 (women, 5.9; men, 4.9). The prevalence ratio was twofold higher in the older age group (p<0.0001)-for men (p=0.034) as well as for women (p<0.001). Conclusions: Prevalence and incidence values of myasthenia gravis from Estonia are similar to those reported in most studies from Europe and north America. However, there seems to be a higher frequency in the elderly (≥50 years) in Estonia.