1. Department of Preventive Dentistry and Dental Public Health
2. Aichi-Gakuin University Junior College, Department of Dental Hygiene, Chikusa-ku, Nagoya, Japan
3. Department of Periodontology, School of Dentistry, Aichi-Gakuin University, 1-100, Kusumoto-cho, Chikusa-ku, Nagoya 464-8650, Japan
4. Department of Internal Medicine, School of Dentistry, Aichi-Gakuin University, 1-100, Kusumoto-cho, Chikusa-ku, Nagoya 464-8650, Japan
5. Aichi Health Promotion Foundation, Kita-ku, Nagoya, Japan
6. University College London, Department of Epidemiology and Public Health, Torrington Place, London, UK