Geographic and climatic factors and multiple sclerosis in some districts of Bulgaria.

The multiple sclerosis (MS) prevalence rates in five districts of Bulgaria were compared with some geographic and climatic factors. In Bulgaria the latitude seems not to be a factor influencing the MS distribution. As to the climatic factors, a negative correlation was obtained between MS prevalence and mean annual sunshine hours as well as between MS prevalence and mean annual temperature. When comparing MS prevalence and mean annual precipitation, the correlation was positive.