Latitudinal variation in MS incidence in Scotland.

AIMS: To explore the effect of latitude on incidence of multiple sclerosis (MS) in Scotland. METHODS: MS case data (2010-2015) was ascertained from the Scottish Multiple Sclerosis Register. Patient's postcode at diagnosis was linked to the Scottish Index of Multiple Deprivation (SIMD). Geographical data from SIMD was converted into latitude and longitude and patients were grouped by latitude band. A linear regression analysis was then performed. MS Cumulative Incidence was compared to population density calculated from SIMD. RESULTS: Latitude was associated with MS Incidence rate. Using a linear regression analysis (r2 = 0.22, p = 0.03), the data predicted an increase in the average MS Incidence of 1.31 cases/100,000 person years per increase in degree latitude. MS Cumulative Incidence rates rise with increasing northern latitude up until 59° north. CONCLUSIONS: We found an increasing incidence of MS with latitude without any relationship to population in Scotland. The reasons for this are likely to be multifactorial.