RESUMO
The frequency of multiple sclerosis (MS) in Greece is still debated. Our previous epidemiological field survey with a cross-check study of MS on March 31, 1984, in the province of Evros in north-eastern Greece showed a prevalence rate of 10.1/100,000. In 1990, Milonas et al. recorded a prevalence rate of 29.5/100,000 in northern Greece. So Greece is classified in the medium-frequency zone according to Kurtzke. This study was performed to estimate the prevalence of MS in the province of Evros and the annual incidence rates from 1974 to 1999. Patients were identified from several sources. A clinical follow-up was performed in 95% of the cases, and, if clinically indicated, new paraclinical examinations were performed and cases classified by Poser's criteria. The prevalence rate of the definite MS cases on December 31, 1999, was 38.9/100,000 and places the area in the high-risk zone. The mean annual incidence measured in 5-year intervals increased from 0.66/100,000 in 1974-1978 to 2.36/100,000 in 1994-1999 (p < 0.01). The increase in prevalence can be attributed to other causes than etiological changes, but the increase in the annual incidence rate indicates the possibility of a variation in risk factors of the disease.