1. Research Unit of Clinical Neuroscience, Neurology, University of Oulu, Oulu, Finland
2. Work Ability and Working Careers, Finnish Institute of Occupational Health, Helsinki, Finland
3. MRC, Oulu University Hospital, Oulu, Finland
4. Neurology, Neurocenter, Kuopio University Hospital, Kuopio, Finland
5. Occupational Health Services, Finnish Broadcasting Company, Helsinki, Finland
6. Department of Public Health, University of Helsinki, Helsinki, Finland
7. VTT Technical Research Centre of Finland Ltd, Tampere, Finland
8. Combinostics Ltd, Tampere, Finland