Multiple sclerosis prevalence in Salta City, Argentina

Multiple Sclerosis (MS) is one of the leading causes of disability in young adults. Its prevalence varies according to different countries. In Argentina there is a wide heterogeneity regarding data published in different areas of the country. Prevalence established in most studies is 17 cases per 100,000 inhabitants; however, most of the available data comes from studies that took place in Buenos Aires. There is little or no information from other provinces, especially from Northwest of Argentina (NOA), where there are no studies of the disease prevalence. The aim of this study is to investigate MS prevalence, phenotypes and epidemiological characteristics in Salta, Argentina, in order to contribute to the current knowledge of MS epidemiology and distribution in our country.

A descriptive, observational, transversal study was carried out in the capital city of Salta. Researchers from all public and private hospitals with a Neurology Department have participated. Private researchers who are well known leaders in demyelinating diseases in the city provided valuable information. Patients who did not have medical control for the past two years as well as patients whose last address was not registered in Salta were excluded.

120 registries were obtained from the four hospitals that participated and from the 12 private researchers. Ten patients were excluded due to overlapping data. The population of the area based on 2010 census was 535,310, so we estimated an MS prevalence 23.8 cases per 100,000 inhabitants (95% CI 20.1-27.4), 24.1 cases per 100,000 inhabitants in female population (95% CI 21.2-28.6) and 18.2 cases per 100,000 inhabitants (95% CI 15.2-21.1) in male population. In our analysis, 64 (58.2%) were female and the average age was 42.1 years. 81.8% are recurrent remitting forms, 16.4% secondary progressive and 1.8% primary progressive.

This is the first study that provides epidemiological data on the prevalence and clinical forms of MS in Salta City as well as in the entire Northwest Region of Argentina(NOA). We estimate a prevalence of 23.8 cases per 100,000 inhabitants, which establishes a moderate risk area for MS.