EPIDEMIOLOGY OF MULTIPLE-SCLEROSIS IN THE COUNTY OF VESTFOLD, EASTERNNORWAY - INCIDENCE AND PREVALENCE CALCULATIONS

The county of Vestfold in the South-eastern part of Norway has undergo ne two incidence and prevalence surveys on multiple sclerosis. The pre valence of definite/probable MS on January 1.1963 was 61.6/100000, Bas ed on the same diagnostic criteria, the present study reports a slight increase in prevalence to 86.4/100000 on January Ist 1983. The averag e annual incidence was calculated for 5 years periods from 1953 to 198 3. The time periods 1953-1962 and 1973-1977 showed age-adjusted incide nce rates between 4.50 and 5.49/100000 while the 10-year period 1963-1 972 showed significantly lower rates. The fluctuating pattern of MS in cidence and prevalence over time supports the view that MS is not a st able disease, and that exogenous factors are influencing the disease p attern.