Department of Epidemiology, School of Public Health, UCLA, Los Angeles, USA & Århus University, Denmark, National Institute of Public Health, University of Southern Denmark, Copenhagen, Denmark, National Institute for Health and Welfare, Finland and Nordic School of Public Health, Stockholm, Stockholm, Sweden, Tampere School of Public Health, University of Tampere, Tampere, Finland, Centre for Epidemiology, The Swedish National Board of Health and Welfare, Stockholm, Sweden, Department of Preventive Medicine, University of Iceland, Reykjavik, Iceland, Department of Public Health and Primary Health Care, University of Bergen, Bergen, Norway, and Statistics Denmark, Research Services, Copenhagen, Denmark