1. Nora Health Care Centre, Örebro County Council, 713 31 Nora, Sweden
2. Department of Occupational and Environmental Medicine, Örebro University Hospital, 701 85 Örebro, Sweden
3. Centre for Health Care Sciences, Örebro University Hospital, P.O. Box 1324, 701 13 Örebro, Sweden
4. School of Health and Medical Sciences, Örebro University, 701 82 Örebro, Sweden