1. School of Health and Social Care, University of Essex , Colchester , UK
2. Research Department of Epidemiology and Public Health, University College London , London , UK
3. Lab 1, School of Public Health and Management, Chongqing Medical University , Chongqing , China
4. Population Research Unit, Faculty of Social Sciences, University of Helsinki , Helsinki , Finland
5. Max Planck—University of Helsinki Center for Social Inequalities in Population Health , Helsinki , Finland