Factors associated with the risk of secondary progression in multiple sclerosis

Objective To investigate factors associated with the risk of secondary progression in relapsing-remitting onset multiple sclerosis (MS). Methods We used Kaplan-Meier survival analyses and a multivariable Cox regression model to estimate the influence of the factors: gender, age at disease onset, use of immunomodulatory drugs (IMD), and clinical manifestation at disease onset on the time to secondary progression in a hospital-based cohort of 571 MS patients with a relapsing-remitting onset. Results Gender and onset manifestation had no significant influence on the timing of secondary progression. A higher age at disease onset was associated with a shorter time to secondary progression (multivariable hazard ratio per year increase: 1.02, 95% CI: 1.01 -1.03). The use of IMD was associated with a longer time to secondary progression (multivariable hazard ratio: 0.30, 95% CI: 0.15 -0.61). Conclusions The inverse relationship between age at disease onset and onset of secondary progression is in keeping with previous natural history studies. The beneficial effect of IMD treatment on the time to secondary progression should be taken as hypothesis-generating rather than as proof of a treatment effect, and needs to be further evaluated in well-designed randomised controlled trials.