1. Department of Neurology; Karolinska University Hospital Huddinge; Stockholm Sweden
2. Neuroimmunology Unit; Centre for Molecular Medicine; Department of Clinical Neuroscience; Karolinska Institute and; Karolinska University Hospital; Solna Stockholm Sweden
3. Clinical Epidemiology Unit and; Centre for Pharmacoepidemiology; Department of Medicine; Karolinska Institute; Karolinska University Hospital; Stockholm Sweden
4. Clinical Epidemiology and Biostatistics; Örebro University Hospital and; Örebro University; Örebro Sweden
5. Department of Epidemiology and Public Health; University College London; London UK