November 22, 2022

Disease-Modifying Therapies Reduce Risk of Conversion from Relapsing-Remitting to Secondary Progressive Multiple Sclerosis

SUMMARY: A population-based nationwide study from Sweden identifies a lower risk of conversion from relapsing-remitting multiple sclerosis (RRMS) to secondary progressive MS (SPMS) after the introduction of disease-modifying therapies (DMTs) in 1995.

The majority of people living with MS are initially diagnosed with RRMS, characterized by periods of relapses in which new symptoms appear or existing symptoms worsen. Over time most people with RRMS will transition to SPMS, a phase of the disease marked by progressive worsening and fewer relapses (read more on the different types of MS – here).

In this study, researchers aimed to determine the impact of the introduction of DMTs on the risk of conversion from RRMS to SPMS at the population level (read more on available DMTs – here). The researchers examined two consecutive nationwide cohorts of people with RRMS from the Swedish MS registry, a database collecting clinical and non-clinical information on Swedish residents diagnosed with MS from over 70 care centres across the country. The first cohort, the ‘untreated group’, consisted of 2161 patients between the period of 1975-1994, prior to the introduction of DMTs and the second cohort consisted of 3510 patients between 1995-2011, after the introduction of DMTs (first-generation injectables) in Sweden, but prior to the availability of second-generation DMTs in 2011.

The researchers found the following:

  • The risk of conversion from RRMS to SPMS was lower in the second cohort who had access to first-generation DMTs, compared to the first cohort who did not have access to DMTs. In people who were untreated, the risk of conversion increased by 3.0% annually. After DMT availability in 1995, the risk of conversion decreased by 2.6% annually.
  • Older age increased the risk of conversion to SPMS up until the age of 50.
  • Age of MS onset affected the risk of conversion to SPMS after the age of 50. The risk of conversion increased for those with older age of MS onset (after 35) and decreased or remained unchanged for those with early age of MS onset (before 35).

This study highlights the benefit of early treatment with DMTs in reducing the risk of conversion to SPMS. Future studies will help to understand the impact of higher efficacy therapies on risk of conversion to progressive MS.

To learn more about the different types of MS and available disease-modifying therapies, visit these pages on the MS Society of Canada website.


Article published in Multiple Sclerosis and Related Disorders on October 5, 2022 – Effectiveness of first generation disease-modifying therapy to prevent conversion to secondary progressive multiple sclerosis. Link to article – here.