Long-term worsening of different body functions in persons with progressive multiple sclerosis

Background: It is unclear whether EDSS is responsive to disability worsening in advanced MS. Objective: To explore the dynamics of disability worsening in persons with advanced-stage MS (EDSS ≥5.5) using three disability worsening definitions (EDSS, Rivermead Mobility Index (RMI), 9-Hole Peg Test (9-HPT)). Methods: EDSS-, RMI- and 9-HPT-based disability worsening were assessed over a minimum of two years in a cohort of 286 persons with advanced MS attending inpatient rehabilitation using Kaplan-Meier Curves and multivariable Cox regression. Furthermore, the correspondence between EDSS-, RMI- and 9-HPT-based disability worsening was analyzed. Results: Disability progression was observed in 49% (9-HPT), 52% (EDSS) and 53% (RMI), with 9-HPT-based worsening slightly lagging behind. The Multiple Sclerosis Severity Score (MSSS) was the only consistent factor predicting disability worsening based on all three definitions (EDSS: hazard ratio 1.48 [1.30;1.68]; RMI: 1.12 [0.99;1.27]; 9-HPT: 1.36 [1.18;1.57]). Correspondence between EDSS and the other definitions (9-HPT and RMI) was 44.3% and 55.7% at time of EDSS progression and 65.1% and 72.5% overall, respectively. Conclusion: In persons with advanced-stage MS, half still developed disability worsening in different functional systems over a median of 6 years. MSSS seems a valid predictor for disability worsening in all three outcome measures in advanced MS.