1 School of Public Health, Department of Epidemiology and International Public Health, Bielefeld University, Bielefeld, Germany, oliver.razum@uni-bielefeld.de.
2 Faculty of Medicine, Department of General Practice & Health Services Research, University of Heidelberg, Heidelberg, Germany and.
3 School of Public Health, Department of Epidemiology and International Public Health, Bielefeld University, Bielefeld, Germany.
4 MRC/CSO Social and Public Health Sciences Unit, University of Glasgow, Glasgow, UK.