1. Department of Medical Psychology, University Medical Center Hamburg-Eppendorf, Germany
2. Section of Health Care Research and Rehabilitation Research, Institute for Medical Biometry and Statistics, Medical Center, University of Freiburg, Faculty of Medicine, Germany
3. Center for Geriatric Medicine and Gerontology Freiburg, Medical Center, University of Freiburg, Faculty of Medicine, Germany
4. Institute for Evidence in Medicine (for Cochrane Germany Foundation), Medical Center, University of Freiburg, Faculty of Medicine, Germany