1. Department of Internal Medicine, University of Turin, Turin, Italy;
2. Cancer Epidemiology Unit, CeRMS and CPO Piemonte, University of Turin, Turin, Italy;
3. Department of Internal Medicine, University of Perugia, Perugia, Italy;
4. Department of Pediatrics, Polytechnic University of Marche, Ancona, Italy;
5. Department of Pediatrics, University of Modena, Modena, Italy;
6. Department of Epidemiology, University of L'Aquila, L'Aquila, Italy;
7. Department of Pediatrics, University of Genova, Genova, Italy;
8. Unit of Observational Epidemiology, Trento, Italy;
9. Università Campus Bio-Medico, University of Rome, Rome, Italy;
10. Department of Pediatrics, University of Napoli, Napoli, Italy;
11. S. Michele Hospital, Cagliari, Italy;
12. Department of Preventive Medicine, University of Pavia, Pavia, Italy;
13. Department of Pediatrics, University of Florence, Florence, Italy;
14. Department of Epidemiology, Biostatistics and Medical Information Technology, Polytechnic University of Marche, Ancona, Italy.