Epidemiology and MS
The first epidemiological studies on multiple sclerosis (MS) around the world pictured a north to south latitudinal gradient. Thus, the north of Europe, north of the USA and Canada were considered high risk areas, while Australia, south of Europe and south of the USA had a medium risk and finally Africa, Asia and central-south America's risk was apparently low. This characteristic distribution led to the first genetic and environmental pathogenic hypothesis.
MS incidence seems to be increasing during the past 20 years based on recent data from prospective studies performed in Europe, America and Asia; specially in women (increased sex ratio). Furthermore, ther are regions that don't seem to fit in the classical gradient, such as Europe, where a similar the MS prevalence in Sardinia (southern Europe) is comparable to Norway.
At present, the study of the epidemiology of MS is a challenge and a great opportunity to determine if there is an increase and a change in the distribution of the disease or if this conclusions are an artifact of the improved diagnostic techniques and the fact that certain areas with previously unknown MS epidemiological data are begining to be studied.
