[1] Hosp Galdakao Usansolo, Unidad Invest, Barrio Labeaga S-N, Galdakao 48960, Biscay, Spain
[2] Red Invest Serv Sanitarios & Enfermedades Cron RE, Madrid, Spain
[3] Hosp Galdakao Usansolo, Serv Cirugia Gen, Galdakao, Biscay, Spain
[4] Corp Parc Tauli, Unidad Epidemiol Clin, Barcelona, Spain
[5] Inst Salud Carlos III, Ctr Nacl Epidemiol, Madrid, Spain
[6] CIBER Epidemiol & Salud Publ CIBERESP, Madrid, Spain
[7] Hosp Costa del Sol, Unidad Invest, Malaga, Spain
[8] Dist AP Sevilla, UDG Salud Publ, Seville, Spain
[9] Hosp Basurto, Unidad Invest, Bilbao, Biscay, Spain
[10] Hosp Donostia Biodonostia, Unidad Invest, Donostia San Sebastian, Gipuzkoa, Spain