Background: Beta interferons (IFN-β) are presently considered one of the best disease-modifying therapies for relapsing-remitting multiple sclerosis (RR MS). Goal: To evaluate, in a group of 80 patients treated for RR MS (50 women, 30 men), the effect of IFN-β using three investigated parameters in patients treated for 12 and 24 months. Methods: Patients were divided into two groups based on treatment duration. The effect of IFN-β on the course of the disease was evaluated with multiple statistical tests, using the criteria of Kurtzke EDSS scale and attack frequency (relapse rate, R/R) 2 years before the beginning of treatment and during the 1. and 2. years of therapy.MRI findings were evaluated with descriptive statistics. Results: In both groups, the differences in average EDSS score during the compared time frame were significant on the p < 0.05 level, while the effect in the group treated for 24 months was detected at the p = 0.0228 level of statistical significance already after 6 months. There were no statistically significant differences in attack frequency between men and women, the paired nonparametricWilcoxon test detected a significant difference in average R/R values after 2 years of IFN-β therapy. InMRimaging, stationary findings predominated.Conclusion:The results of statistical evaluation of the effect of beta interferons on the disease course are favourable and support their long-term use in the corresponding patients.

        Key words: relapsing-remitting multiple sclerosis, β-interferon therapy, statistical analysis of treatment effects