The effect of interferon (IFN) beta-1a (44 and 22 μg subcutaneously [sc] three times weekly [tiw]) on cognition in mildly disabled patients with relapsing-remitting multiple sclerosis (McDonald criteria; Expanded Disability Status Scale =4.0) was assessed by validated neuropsychological testing at baseline and at regular intervals for up to 2 years in this ongoing open-label, 3-year study. Year-2 data were available for 356 patients (22 μg, n = 175; 44μg, n = 181). The proportion of patients with impaired cognitive function was stable during the study: 21.4% at baseline and 21.6% at 2 years. At 2 years, the proportion of patients with =3 impaired cognitive tests was significantly lower in the 44 μg treatment group (17.0%) compared with the 22 μg group (26.5%; p = 0.034), although there was already a trend towards a higher proportion of patients with cognitive impairment in the 22 μg group at baseline. Factors associated with impairment in = three cognitive tests after 2 years were age (odds ratio [OR]: 1.05; 95% confidence interval [CI]: 1.00-1.09), verbal intelligence quotient (OR: 0.95; 95% CI: 0.92-0.98), and having = three impaired cognitive tests at baseline (OR: 11.60; 95% CI: 5.94-22.64). These interim results show that IFN beta-1a sc tiw may have beneficial effects on cognitive function as early as 2 years after treatment initiation, but the final 3-year data of the study are required to confirm these results.
Keywords: cognitive function; cognitive impairment; interferon beta-1a; relapsing-remitting multiple sclerosis.