More than 90,000 Canadians live with multiple sclerosis (MS) a chronic disease affecting the brain and central nervous system. It often affects young adults, with diagnosis generally occurring between 25 and 45 years of age. For those seeking to understand how MS affects individuals and populations, Canadian health data offers a wealth of information for researchers, with findings of relevance to all Canadians. Epidemiological data captured across Canada has, for many years, informed research and care across the country and, sometimes, in the United States (US).

An international group of researchers, including Dr. Helen Tremlett at the University of British Columbia, have formed a Multiple Sclerosis (MS) Prevalence Working Group to assess the feasibility of using population data in the US to determine how many people have MS. There had not been a comprehensive, national study of MS prevalence since 1975. In a trio of papers published online on  February 15, 2019, in Neurology, the medical journal of the American Academy of Neurology, the Working Group has outlined new findings, filling key American knowledge gaps.

Dr. Helen Tremlett’s research and the Working Group have been supported by the National Multiple Sclerosis Society (USA). Relying on Canadian data has informed much of our understanding of MS in North America, but without a clear picture of MS in the US it is hard to know the scope of the disease and the burden on Americans and their families. Dr. Tremlett has worked with the National MS Society for the past five years to facilitate this endeavour and provide a Canadian researchers’ perspective.

According to a bulletin released from the National MS Society in conjunction with the Neurology trio, the Society launched the MS Prevalence Initiative in 2014 to determine the best way to develop a scientifically sound and economically feasible estimate of the number of people in the US who have MS.

This initiative included leading experts in MS epidemiology, statistics and healthcare, who used administrative datasets from a variety of American sources, and included population-based health data in Canada in order to validate findings and assess reliability.

They found that rates of MS in the US are nearly double previous estimates.

To determine MS rates in the US, the team developed an algorithm to detect MS cases in population health data sets. The information came from both American and Canadian sources, and included prescription use and physician and hospital records in order to reliably assess the prevalence of MS rates across the USA.

There was clear evidence for a north-south gradient in terms of MS prevalence, with northern US states showing higher rates of the disease than southern states.

“Our method to reliably estimate the prevalence of MS in the US is a major step forward. This approach allows a far more comprehensive picture of MS in the USA. The algorithm we developed can be readily used by others to better understand MS, including the economic burden of MS, and will facilitate the monitoring and mapping of MS prevalence over time. It might even help provide clues as to what causes MS in the future. Ultimately, we hope findings will improve outcomes for all people living with MS,” said Dr. Tremlett.