University of Bergen/The Norwegian MS Competence Centre, Haukeland University Hospital, Norway kristin.wesnes@gmail.com. University of Bergen/The Norwegian MS Competence Centre, Haukeland University Hospital, Norway. Section of Clinical Neurology, University of Ferrara, Italy. Clinic of Neurology, Faculty of Medicine, University of Belgrade, Serbia. Institute of Clinical Medicine, Faculty of Medicine, University of Oslo/Akershus University Hospital, Norway. University of Tromsø/University Hospital of North Norway, Norway. Division of Neurology, Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden. Darmstadt, Germany. Institute of Clinical Medicine, Faculty of Medicine, University of Oslo/Institute of Immunology, Oslo University Hospital Rikshospitalet, Norway. Department of Epidemiology and Biostatistics and occupational health, McGill University, Montreal, Canada. Institute of Epidemiology, Faculty of Medicine, University of Belgrade, Serbia. Research institute of the McGill University Health Centre, Montreal, Canada. University of Bergen, Norway/ Department of Clinical and Experimental Medicine, University of Sassari, Italy. The Norwegian MS Competence Centre, Haukeland University Hospital/The KG Jebsen Centre for MS-Research, University of Bergen, Norway.