1. Department of Pediatrics, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark/Department of Neurology, Herlev Hospital, Copenhagen, Denmark
2. Danish Multiple Sclerosis Center, Department of Neurology, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
3. National Institute of Public Health, University of Southern Denmark, Copenhagen, Denmark
4. Section of Biostatistics, Department of Public Health, University of Copenhagen, Copenhagen, Denmark
5. Danish Multiple Sclerosis Center, Department of Neurology, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark/Danish Multiple Sclerosis Registry, Department of Neurology, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark