1. Gastroenterology Department, Clinical University Hospital of Ferrol , Ferrol , Spain
2. University of Santiago de Compostela , Santiago de Compostela , Spain
3. Department of Preventive Medicine and Public Health, University of Santiago de Compostela , Santiago de Compostela , Spain
4. CIBER de Epidemiología y Salud Pública (CIBERESP) , Madrid , Spain
5. Clinical University Hospital of Santiago de Compostela , Santiago de Compostela , Spain