1. Department of Primary Care and Medical Education, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Kita-ku, Okayama, Japan;
2. Department of Human Ecology, Okayama University Graduate School of Environmental and Life Science, Kita-ku, Okayama, Japan;
3. Department of Epidemiology and Preventive Medicine, Gifu University Graduate School of Medicine, Yanagido, Gifu City, Japan;
4. Department of Epidemiology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Kita-ku, Okayama, Japan