Changes in the impact of MS on cognitive functioning and fatigue over 12 natalizumab infusions. (A) Mean MOS-Cog (± SE) and (B) MFIS-5 scores (± SE) at baseline prior to natalizumab initiation and after the 3rd and 12th infusion. Because of missing data for covariates in their respective models, n values for MOS-Cog were 331 and 333 for MFIS-5. p values were from analyses of variance performed on the adjusted means estimated by the mixed effect model controlling for infusion, age, baseline DS, baseline FS, years since diagnosis, and infusion, age, baseline DS, baseline FS, number of comorbidities for MOS-Cog, and number of MS drugs taken prior to natalizumab for MFIS-5. (C) Proportion of patients with improved, stable, or worsened cognitive functioning (MOS-Cog) and fatigue (MFIS-5). MFIS-5 and MOS-Cog scores had to change by at least one score point to be considered changed. *p < .0001. DS Disease Steps; FS Functional Status; MFIS Modified Fatigue Impact Scale - 5 items; MOS-Cog Medical Outcomes Scale-Cognitive Functioning; SE standard error.