Investigation of heterogeneity in the association between interferon beta and disability progression in multiple sclerosis: an observational study A Shirani, Y Zhao, ME Karim, J Petkau, P Gustafson, C Evans, E Kingwell, ML {van der Kop}, J Oger, H Tremlett January 2014 Source Document multiple-sclerosis longitudinal-data observational-data survival-analysis Related Marginal structural Cox models for estimating the association between beta-interferon exposure and disease progression in a multiple sclerosis cohort Interferon beta and long-term disability in multiple sclerosis Association between use of interferon beta and progression of disability in patients with relapsing-remitting multiple sclerosis