1. Admission and Documentation Service, University Hospital Complex of a Coruña, Spain
2. Department of Preventive Medicine and Public Health, University of Santiago de Compostela, Spain
3. CIBER de Epidemiología y Salud Pública, CIBERESP, Spain
4. Department of Epidemiology, Brown School of Public Health, Brown University, Providence, Rhode Island, USA
5. Service of Neumology, University Hospital Complex of Vigo, Vigo, Spain
6. Service of Neumology, Ourense Hospital Complex, Ourense, Spain
7. Service of Neumology, University Hospital Complex of A Coruña, Coruña, Spain
8. Oncologic Hospital, A Coruna, Spain
9. Service of Neumology, Hospital Lucus Augusti, Lugo, Spain
10. Service of Neumology, Santiago de Compostela University Clinic Hospital, Santiago de Compostela, Spain
11. National Institute of Silicosis, University Hospital of Asturias, Asturias, Oviedo, Spain
12. Service of Oncology, Puerta de Hierro University Hospital, Madrid, Spain
13. Service of Neumology, Hospital Arquitecto Marcide, Ferrol, Spain
14. Service of Neumology. Hospital Complex of León, León, Spain
15. Service of Preventive Medicine, University Hospital Complex of Santiago de Compostela, Spain