Subcutaneous Interferon b-1a May Protect against Cognitive Impairment in Patients with Relapsing–Remitting Multiple Sclerosis: 5-Year Follow-up of the COGIMUS Study

Objective: To assess the effects of subcutaneous (sc) interferon (IFN)-1a on cognition over 5 years in mildly disabled patients with relapsing–remitting multiple sclerosis (RRMS). Methods: Patients aged 18–50 years with RRMS (Expanded Disability Status Scale score #4.0) who had completed the 3-year COGIMUS study underwent standardized magnetic resonance imaging, neurological examination, and neuropsycho-logical testing at years 4 and 5. Predictors of cognitive impairment at year 5 were identified using multivariate analysis. Results: Of 331 patients who completed the 3-year COGIMUS study, 265 participated in the 2-year extension study, 201 of whom (75.8%; sc IFN b-1a three times weekly: 44 mg, n = 108; 22 mg, n = 93) completed 5 years ’ follow-up. The proportion of patients with cognitive impairment in the study population overall remained stable between baseline (18.0%) and year 5 (22.6%). The proportion of patients with cognitive impairment also remained stable in both treatment groups between baseline and year 5, and between year 3 and year 5. However, a significantly higher proportion of men than women had cognitive impairment at year 5 (26.5 % vs 14.4%, p = 0.046). Treatment with the 22 versus 44 mg dose was predictive o