1. Department of Epidemiology Research, Statens Serum Institut, Copenhagen, Denmark
2. Focused Research Unit in Neurology; Department of Neurology, Hospital of Southern Jutland, University of Southern Denmark, Denmark
3. The Danish Multiple Sclerosis Registry, Department of Neurology, Rigshospitalet, Copenhagen, Denmark
4. Institute of Regional Health Research, University of Southern Denmark, Odense, Denmark
5. Multiple Sclerosis Clinic of Southern Jutland (Sønderborg, Kolding, Esbjerg), Department of Neurology, Sønderborg, Denmark
6. National Institute of Public Health, University of Southern Denmark, Copenhagen, Denmark
7. Department of Clinical Epidemiology, Clinical Institute, University of Aarhus, Aarhus, Denmark
8. Danish Multiple Sclerosis Center, Department of Neurology, University of Copenhagen, Rigshospitalet, Copenhagen, Denmark
9. Department of Medicine, Stanford University School of Medicine, Stanford CA USA 94305