1. Institute for Social Medicine, Epidemiology and Health Economics; Charité Hospital, Humboldt University of Berlin, D-Berlin, Germany
2. Institute for Social Medicine, Epidemiology and Health Economics; Charité Hospital, Humboldt University of Berlin, D-Berlin, Germany
3. Karl and Veronica Carstens-Foundation, D-Essen, Germany
4. Institute for Social Medicine, Epidemiology and Health Economics; Charité Hospital, Humboldt University of Berlin, D-Berlin, Germany