Background The Atlas of MS is the most extensive worldwide study of the epidemiology of MS and the global availability and accessibility of resources for people with MS. Findings from the 2008 and 2013 editions have been widely cited by the global MS research, advocacy, and policy communities.
Objectives The third edition of the Atlas of MS aimed to gather more comprehensive data regarding the global prevalence of MS. Valid data regarding the worldwide distribution of MS will enable decision makers to improve healthcare policy and allocate resources to better meet the needs of people with MS, their caregivers, and families.
Methods Between September 2019 and March 2020, country coordinators completed a questionnaire to report the most recent epidemiologic data available about MS in their country. The questionnaire was available in multiple formats and languages (i.e., English, French, and Spanish). Country coordinators were encouraged to work with appropriate experts to gather data and were asked to provide information on data sources where possible. The global prevalence estimate was calculated using either the country-provided data or an imputed value calculated from available reported data. Countries were grouped into the six World Health Organization (WHO) regions and the four World Bank income levels for analysis.
Results Data were gathered from 115 countries (104 provided prevalence), accounting for 87% of the world population. The estimated MS prevalence among the participating countries ranged from less than 1 up to 337 per 100,000 persons. Using imputed estimates for countries without data, the estimated number of people living with MS worldwide is 2.8 million (prevalence = 35.9), an increase of 470,000 from the 2013 estimate. The European (133.0) and American (111.7) regions had the highest overall prevalence estimates, while the African (5.3) and Western Pacific (4.8) had the lowest. High income level countries reported higher prevalence estimates compared to countries with lower income levels.
Conclusions The worldwide number of people with MS has increased by at least 20% since the 2013 estimate of 2.3 million. Reasons for the increase are not known, but likely include population growth, improved reporting, increased MRI availability, earlier diagnosis and longer survival. It is likely that the prevalence estimate is an underestimate of the actual prevalence of MS worldwide because there is poor or limited surveillance data in many countries.