1. Department of Physical Medicine and Rehabilitation, Oslo University Hospital, Oslo, Norway
2. Faculty of Health Sciences, Oslo Metropolitan University, Oslo, Norway
3. Faculty of Medicine, University of Oslo, Oslo, Norway
4. Oslo Centre of Biostatistics and Epidemiology, Research Support Services, Oslo University Hospital, Oslo, Norway
5. Department of Research, Statped, Oslo, Norway
6. Sunnaas Rehabilitation Hospital, Nesoddtangen, Norway