Rates of progression vary widely in PPMS. This study  aimed to
identify predictors of progression over 10 years. A total of 101
patients who had been imaged at baseline and 2 years were scored on the EDSS after 10 years. The study identified the following things that
predicted progression: male sex, shorter disease duration, and slower
timed walk test at baseline (best overall predictor), and deterioration
in EDSS score and reduction in brain volume over 2 years.