The Effect of Treatment Exposure on Disability Risk in Relapsing-Remitting MS

Although the short-term effects of disease-modifying treatments (DMTs) for multiple sclerosis (MS) have been established, their long-term impacts remain unknown. A study evaluated how treatment exposure correlates with disability risk in patients with relapsing-remitting MS. The authors concluded that long-term treatments provide more beneficial cumulative impact compared with short-term treatments alone.

The retrospective, observational cohort study consisted of data from four French MS expert centers taking part in the French MS database; the present analysis consisted of 2,285 adult patients. The main outcomes were irreversible Expanded Disability Status Scale 4 (EDSS4) and conversion to secondary progression of MS (SPMS).

The mean age at baseline was 33.4 years (standard deviation, 8.9 years). Three-quarters of the cohort was female. Patients with 15-year continuous treatment starting 20 years ago, compared with those with five-year treatment starting 10 years ago, had a 26% decreased risk for EDSS4 and 34% decreased risk for SPMS. As duration of exposure to DMT increased, the risk for disability decreased.

“This study found that not only the moment when a treatment is initiated is important but that the amount of time spent on treatment is also a strong decisive factor for its overall effectiveness. We show that combined effect of early and long-term use of DMT was protective and accumulated over time. The risk of disability (moderate irreversible disability or SPMS) decreased with increasing duration of exposure to DMT and this duration had a stronger impact than early use,” the study authors concluded.