Comparison of statistical approaches for dealing with immortal time bias in drug effectiveness studies ME Karim, P Gustafson, J Petkau, H Tremlett, {BeAMS} January 2016 PDF Code Source Document marginal-structural-model causal-inference multiple-sclerosis longitudinal-data observational-data survival-analysis immortal-time-bias simulation theory Related Marginal structural Cox models for estimating the association between beta-interferon exposure and disease progression in a multiple sclerosis cohort Association between use of interferon beta and progression of disability in patients with relapsing-remitting multiple sclerosis Beta-interferon exposure and onset of secondary progressive multiple sclerosis Multiple sclerosis in older adults: the clinical profile and impact of interferon beta treatment Investigation of heterogeneity in the association between interferon beta and disability progression in multiple sclerosis: an observational study