FUNDING COSMOS is sponsored by the Bone and Mineral Research Unit (Hospital Universitario Central de Asturias), SAFIM (Sociedad Asturiana Fomento Investigaciones O´ seas), the European Renal Association–European Dialysis and Transplant Association, the National Program of I þ D þ I 2008–2011 and Instituto de Salud Carlos III (ISCIII), the ISCIII Retic REDinREN (RD06/0016/1013, RD12/0021/0023 and RD16/ 0009/0017), the ISCIII (ICI14/00107, PI17/00384 and PI20/ 00633), Fondo Europeo de Desarrollo Regional (FEDER), Plan Estatal de I þ D þ I 2013–2016, Plan de Ciencia, Tecnologia e Innovacion 2013–2017 y 2018–2022 del Principado de Asturias (GRUPIN14-028, IDI-2018-000152), Fundacio´n Renal I ´nigo A ~ ´ lvarez de Toledo (FRIAT) and the Spanish Society of Nephrology (Estudio Estrate´gico de la SEN). Logistics (meetings, secretarial help, printing of materials, development of website for data entry, etc.) have been financially supported by AMGEN Europe and FRIAT. The authors are not aware of any additional relationships, funding or financial holdings that might be perceived as affecting the objectivity of this study. COSMOS participating centres: see Supplementary Appendix.Background. Besides advances in haemodialysis (HD), mortality rates are still high. The effect of the different types of HD membranes on survival is still a controversial issue. The aim of this COSMOS (Current management Of Secondary hyperparathyroidism: a Multicentre Observational Study) analysis was to survey, in HD patients, the relationship between the use of conventional low- or high-flux membranes and all-cause and cardiovascular mortality. Methods. COSMOS is a multicentre, open-cohort, 3-year prospective study, designed to evaluate mineral and bone disorders in the European HD population. The present analysis included 5138 HD patients from 20 European countries, 3502 randomly selected at baseline (68.2%), plus 1636 new patients with <1 year on HD (31.8%) recruited to replace patients who died, were transplanted, switched to peritoneal dialysis or lost to follow-up by other reasons. Cox-regression analysis with timedependent variables, propensity score matching and the use of an instrumental variable (facility-level analysis) were used. Results. After adjustments using three different multivariate models, patients treated with high-flux membranes showed a lower all-cause and cardiovascular mortality risks fhazard ratio (HR) = 0.76 [95% confidence interval (CI) 0.61-0.96] and HR = 0.61 (95% CI 0.42-0.87), respectivelyg, that remained significant after matching by propensity score for all-cause mortality (HR = 0.69, 95% CI 0.52-0.93). However, a facility-level analysis showed no association between the case-mix-adjusted facility percentage of patients dialysed with high-flux membranes and all-cause and cardiovascular mortality. Conclusions. High-flux dialysis was associated with a lower relative risk of all-cause and cardiovascular mortality. However, dialysis facilities using these dialysis membranes to a greater extent did not show better survival.publishersversionpublishe
