[Prevalence and incidence of multiple sclerosis in the province of Parma, 1965-1980. Preliminary data].

Recent epidemiological studies in small communities report very high prevalence rates of multiple sclerosis (MS), suggesting that Italy should be included among high risk areas for MS. Such data are not confirmed when populations exceeding 300.000 are considered. The total prevalence rate of probable MS in the province of Parma was 23.07 per 100.000 on the prevalence day Dec. 31, 1980. Up to date, very few studies deal with incidence of MS, due to the fact that in many cases it is difficult to establish the exact outburst of the disease. Yet, incidence will indicate the real risk for the disease for a given period in a more accurate manner. Mean annual incidence of MS in the province of Parma in the period 1965-80 was 1.14 per 100.000. A previous survey in the period 1950-59 reported, for the same area, an incidence rate of 1.01 per 100.000, versus a prevalence rate of 12.33 per 100.000. In our opinion, when comparison of data between two different areas, in different periods, is to be made, incidence rates for MS should be preferred to prevalence studies.