1 Department of Preventive Medicine and Public Health, University of Santiago de Compostela, Santago de Compostela 15782, Spain; CIBER de Epidemiología y Salud Pública (CIBERESP), Spain. Electronic address: alberto.ruano@usc.es.
2 Department of Preventive Medicine and Public Health, University of Santiago de Compostela, Santago de Compostela 15782, Spain; CIBER de Epidemiología y Salud Pública (CIBERESP), Spain.
3 Servicio de Neumología, Hospital Universitario Central de Asturias, Oviedo, Spain.
4 Service of Oncology, Hospital Puerta de Hierro, Madrid, Spain.