Nils Koch-Henriksen1, Klaus Lauer2. 1. From The Danish Multiple Sclerosis Registry (N.K.-H.), Copenhagen University Hospital, Rigshospitalet; Department of Clinical Epidemiology (N.K.-H.), University of Aarhus, Denmark; and private practice (neuroepidemiologist, K.L.), Griesheim, Germany. koch-henriksen@stofanet.dk. 2. From The Danish Multiple Sclerosis Registry (N.K.-H.), Copenhagen University Hospital, Rigshospitalet; Department of Clinical Epidemiology (N.K.-H.), University of Aarhus, Denmark; and private practice (neuroepidemiologist, K.L.), Griesheim, Germany.