1. THL National Institute for Health and Welfare, P.O. BOX 30, 00271 Helsinki, Finland, , Nordic School of Public Health, Gothenburg, Sweden
2. Department of Public Health, University of Helsinki, Helsinki, Finland
3. National Institute of Public Health, University of Southern Denmark, Copenhagen, Denmark
4. Faculty of Social Science, Vestfold University College, Tønsberg, Norway
5. Department of Medical Epidemiology and Biostatistics, Karolinska Institute, Stockholm, Sweden
6. Division of Epidemiology, University of Southern Denmark, Denmark, Odense, Denmark
7. THL National Institute for Health and Welfare, P.O. BOX 30, 00271 Helsinki, Finland