[The prevalence of multiple sclerosis in the city of Ourense, Galicia, in the north-west of the Iberian Peninsula].

Introduction: Multiple sclerosis is an inflammatory neurodegenerative disease of the central nervous system, which mainly affects young people of working and reproductive age, and represents the first cause of non-traumatic disability in this age group of the population. A north-south latitude gradient is recognised, with prevalence rates increasing as we move away from the equator. This gradient probably represents the genetic predisposition transmitted from the Scandinavian regions through the Viking invasions and could presuppose an influence of the vitamin D deficit related to a lower number of hours of sunshine per year.

Aims: To determine the prevalence and incidence of multiple sclerosis in the city of Ourense, Galicia.

Patients And Methods: The latitude coordinate of the city of Ourense is 42° 34' N. A retrospective epidemiological study covering the period from 2002 to 2016 was conducted. The prevalence date was 31 December 2016. According to the latest census, the population of the city of Ourense was 105,892 on 1 January 2016.

Results: Altogether, 195 cases were recorded, representing a prevalence of 184.1 cases/100,000 inhabitants. In the period 2002-2016, 127 cases of multiple sclerosis were diagnosed, representing an average incidence of 7.86 cases/100,000 inhabitants/year.

Conclusion: The city of Ourense has the highest prevalence rate of multiple sclerosis of those studied to date in the Iberian Peninsula, with a figure that brings it closer to the data reported in more northern areas under Nordic and Anglo-American influence.