Epidemiology of multiple sclerosis in western Poland--a comparison between prevalence rates in 1965 and 1981.

An epidemiological survey of multiple sclerosis was carried out in the western part of Poland. The estimated prevalence rate on December 31, 1981 was compared with that established on the same territory on January 1, 1965. The disease was less frequent in 1981. The prevalence rate for definite cases was only 42.87 versus 51.19. A marked increase of population in the younger age groups (those under 20) during the last decade may account for the observed differences in the prevalence rate. In the town of Gniezno, a new MS cluster with a prevalence rate of 118.10 per 100,000 population was discovered.