Effect of relapses over early progression of disability in multiple sclerosis patients treated with beta-interferon

Observational study designed to explore the effect of demographical variables and number of relapses over the disability progression in the two first years of beta-interferon treatment for multiple sclerosis. One hundred and sixty two patients treated with beta-interferon for at least two years were included, 70.9% females, mean age 33.4 years, mean disease duration 75.1 months, mean EDSS 2.4, previous year relapse rate 1.3. Main end-point was defined as a sustained EDSS increase (1.5 if previous EDSS 0-2.0; 1.0 if previous EDSS 2.5-4.0; 0.5 if previous EDSS 4.5 or higher). 62.3% of patients presented one or more relapses and 32.7% patients reached sustained disability increase. The univariate and multivariate Cox regression analysis only showed statistical significance for the relapses in the two first years after the treatment (HR 1 relapse: 3.4, p = 0.05; HR > or = 2 relapses: 4.3, p < 0.001). The Kaplan-Meier survival analysis showed a higher probability of EDSS progression for patients with one relapse (log rank 10.9, p = 0.02) and with > or = 2 relapses (log rank 17.7, p < 0.001), with no differences between them (p = 0.38). In conclusion, patients with one or more relapses in the first two years of interferon treatment developed an earlier sustained progression of the disability.