1. Institute for Health Services Research and Health Economics, Centre for Health and Society, Medical Faculty and University Hospital Düsseldorf; Heinrich-Heine-University; Düsseldorf Germany
2. Department of Geriatrics; Parc de Salut Mar; Barcelona Spain
3. Physical Medicine and Rehabilitation (MFRHB); Hospital de la Santa Creu i Sant Pau; Barcelona Spain
4. Institute of Health and Nursing Sciences, Medical Faculty; Martin Luther University Halle-Wittenberg; Halle (Saale) Germany