Prevalence of multiple sclerosis in the Sanitary District of Calatayud, northern Spain: Is Spain a zone of high risk for this disease?

We undertook an epidemiologic study to ascertain the prevalence of multiple sclerosis (MS) in the Sanitary District of Calatayud, in the north-east of Spain. Methods: The study was performed from October 1990 to July 1996. The total number of residents in the area was 58,591. an extensive search was carried out to identify all cases of known or suspected MS through general practitioners and specialists, sanitary authorities in the area, the reference hospital, the Spanish Multiple Sclerosis Society, the newspaper and radio. Results: April I, 1995 was chosen as prevalence day. The crude prevalence rate for the area was 58 per 100,000 (95% CI: 39-78). The approximate annual incidence rate was 2.6/100,000 (1980-1989). Conclusions: This study and others conducted recently in Spain show that MS is more prevalent than was previously thought and afflicts at least 53-65 per 100,000 population.