The effects of long-term interferon-beta-1b treatment on cognitive functioning in multiple sclerosis: a 16-year longitudinal study

Background: Multiple sclerosis (MS) is a progressive disease of the central nervous system that affects cognition. Shortterm treatment with interferon‐beta‐1b (IFN‐beta‐1b) has been shown to have beneficial effects on cognition. Objective: The objective of this paper is to evaluate the effects of IFN‐beta‐1b on cognitive functioning in patients with MS over the course of 16 years. Methods: Sixteen subjects with relapsing‐remitting MS participated in the study. Nine of these subjects received IFNb‐ 1b, while seven received placebo treatment in the pivotal MS trial. After five years, all subjects were switched to IFNb‐ 1b treatment. At two and four years into the study, all subjects underwent a brief neuropsychological test battery, magnetic resonance imaging (MRI), and neurologic ratings; measures were repeated at 16 years. Results: Across the total cohort, cognitive functioning remained relatively stable over the course of 16 years. The placebo/IFN‐beta‐b group exhibited increased visual memory performance relative to the IFN‐beta‐1b treatment group, but had a greater decline in verbal memory. Initial MRI lesion load demonstrated a significant, negative correlation with overall cognitive performance at 16 years (p = 0.00). Conclusion: We conclude that IFN‐beta‐1b has beneficial effects on long‐term cognition outcomes in MS.