Effects of interferon beta-1b on cognitive performance in patients with a first event suggestive of multiple sclerosis

Background: Cognitive dysfunction occurs at the earliest stages of multiple sclerosis (MS), including the stage of clinically isolated syndrome (CIS). Methods: We evaluated the impact of interferon beta-1b (IFNβ-1b) 250 µg on cognitive performance during the CIS stage in the BENEFITstudy. Cognition was assessed by Paced Auditory Serial Addition Test-3” (PASAT-3”) scores. Results: Improvement in PASAT-3” score from baseline to year two was greater for IFNβ-1b treatment than placebo in patients not reaching clinically definite MS (CDMS) by year two. The treatment effect was maintained at year five and was statistically significant. Conclusions: To conclude, early IFNβ-1b treatment had a sustained positive effect on PASAT-3” score over the 5-year BENEFIT study.