1. Department of Epidemiology and Public Health, University College London, London, UK
2. Clinical Epidemiology and Biostatistics, School of Medical Sciences, Örebro University, Örebro, Sweden
3. Department of Health and Social Behavior, School of Public Health, University of Tokyo, Tokyo, Japan
4. Division of International and Community Oral Health, Graduate School of Dentistry, Tohoku University, Miyagi, Japan
5. Department of Statistics, Örebro University, Örebro, Sweden
6. Center for Preventive Medical Science, Chiba University, Chiba, Japan