1. Department of Medical Sociology, Heinrich-Heine-University, Universitätsstrasse 1 Duesseldorf 40225, Germany,
2. Department of Medical Sociology, Heinrich-Heine-University, Universitätsstrasse 1 Duesseldorf 40225, Germany
3. Institute of Social and Preventive Medicine, University of Bern, Switzerland
4. Social Medicine, CAPHRI, Maastricht University, Netherlands