Digital epidemiology confirms a latitude gradient of MS in France

Background: A gradient of prevalence of MS has been previously reported, and this may be due to different environmental and genetic features of the different populations, but also to methodological issues. In France, for example, three studies analysed the presence of such a gradient with conflicting results. The aim of this study was to assess whether digital epidemiology could confirm the presence of such a gradient. Methods: through Google Trends, we analysed the relative search volume (RSV) for ‘multiple sclerosis’ in France, from 2004 to 2017, and assessed if an association with the decimal degree of latitude existed. Results: Latitude was correlated with crude RSV (r2 0.39, p 0.04) in the 21 regions considered, with a southwest/northeast gradient. A multiple linear regression model adjusted for sex and age confirmed the existence of such a latitudinal effect, with an increase of 2.43 RSV units for each unit increase in latitude (95% CIs 0.62–4.24, p < 0.01, adjusted r2 0.61). Conclusions: our study provides additional evidence for the existence of a latitude gradient in MS, and the value of Internet-acquired data as real-time surveillance tools and alerts for healthcare systems.