Incidence of multiple sclerosis in Chile. A hospital registry study

Abstract

Objective - To study the incidence of MS in Chile by examining the hospitalizations across all geographical regions of the country and to examine whether there is a correlation between these rates and the latitude or ultraviolet radiation. Methods - This is a descriptive study examining the national registry of hospitalizations because of MS (code G35 in ICD-10) from January 1, 2001, to December 31, 2006. Incidence rates were calculated by gender and geographical region and standardized to the world population estimated for 2010. Results - A total of 6857 hospitalizations were analyzed. There were 935 individuals; 63.9% were women. The mean incidence rate for 2002-2006 period was 0,90 (95% CI: 0.75-1.05). The annualized incidence rates for regions from North to South were as follows: I Tarapaca 0.54 (95% CI: 0.0-1.21), II Antofagasta 0,93 (0.10-1.75), III Atacama 1.07 (0.0-2.31), IV Coquimbo 0.63 (0.01-1.24), V Valparaiso 0.83 (0.38-1.27), VI O'Higgins 0.72 (0.14-1.30), VII Maule 0.52 (0.06-0.98), VIII BIO BIO 0.81 (0.41-1.21), IX Araucania 0.43 (0.0-0.86), X Los Lagos 0.91 (0.35-1.46), XI Aysen 0.99 (0.0-2.98), XII Magallanes 3.54 (0.57-6.51), and XIII Metropolitana 1.10 (0.84-1.36). There were no significant correlations between hospitalization rates and latitude, except for region XII. UV radiation levels showed significant differences only for region XII. Conclusion - There is a moderate risk of MS in Chile. The southernmost region showed significantly higher incidence rates than those in the rest of the country (a cluster zone). We did not find any correlation between incidence rates and latitude or UV radiation.