1. Department of Neurology; Danish Multiple Sclerosis Center; Rigshospitalet; University of Copenhagen; Copenhagen Denmark
2. Department of Neurology; The Danish Multiple Sclerosis Registry; Rigshospitalet; Copenhagen Denmark
3. Department of Clinical Epidemiology; Clinical Institute; University of Aarhus; Aarhus Denmark
4. The Danish National Institute of Public Health; University of Southern Denmark; Copenhagen K Denmark