1. Periodontology Unit and Department of Clinical Research (L.N., N.T., I.N., F.D., N.D.), London WC1X 8LD, United Kingdom
2. International Centre for Evidence-based Oral Health (I.N.), University College London Eastman Dental Institute, London WC1X 8LD, United Kingdom
3. Graduate Institute of Epidemiology and Preventive Medicine (Y.-K.T.), College of Public Health, National Taiwan University, Taipei 10617, Taiwan
4. Department of Internal Medicine (M.R.), University of Palermo, 90133 Palermo, Italy
5. Euro-Mediterranean Institute of Science and Technology (M.R.), 90133 Palermo, Italy