Can we measure long-term treatment effects in multiple sclerosis?

The short-term safety and efficacy of IFN-β in patients with multiple sclerosis are well established, but less is known about this drug when taken over years and decades. Sormani and Bruzzi discuss the difficulties associated with designing studies of the long-term treatment effects of IFN-β. They then present techniques that have been employed to minimize potential sources of bias. The authors conclude that long-term use of IFN-β reduces clinical progression, but important questions relating to mortality warrant further investigation.