Scott TF, et al. - Using long-term data collected in the clinic, researchers identified the contribution of relapse-associated disability to overall disability in relapse-onset multiple sclerosis (RMS). Records were screened for inclusion in this study for all newly diagnosed patients with relapse-onset MS who attended the center from 1989 to 2005 and met the McDonald criteria for an MS diagnosis. A retrospective study was conducted of a cohort of newly diagnosed RMS patients (n = 176), measuring all confirmed disability changes up to 15 years after the onset. Worsening was evaluated annually and in 5-year epochs and was attributed to either relapse (RW) or slow progression (PW). Over time, RW was less frequent, but accounted for most changes in Expanded Disability Status Scale in the first decade of MS, and remained important even in years 11-15. Median disability change due to RW vs PW over the entire 15 years has been similar. During the first 15 years after onset, the worsening of treated MS was linked to relapses in many RMS patients, indicating an opportunity for long-term benefit through the reduction of relapse.