Association between CKD-MBD and mortality in older patients with advanced CKD—results from the EQUAL study

Background: Chronic Kidney Disease-Mineral and Bone Disorder (CKD-MBD) is a common complication of CKD, associated with higher mortality in dialysis patients, while its impact in non-dialysis patients remains mostly unknown. We investigated the associations between parathyroid hormone (PTH), phosphate, and calcium (and their interactions) and all-cause, cardiovascular (CV), and non-CV mortality in older non-dialysis patients with advanced CKD. Methods: We used data from the European Quality study, which includes patients aged ≥65 with eGFR ≤20 ml/min/1.73 m2 from six European countries. Sequentially adjusted Cox models were used to assess the association between baseline and time-dependent CKD-MBD biomarkers and all-cause, CV, and non-CV mortality. Effect modification between biomarkers was also assessed. Results: In 1294 patients, the prevalence of CKD-MBD at baseline was 94%. Both PTH (aHR 1.12, 95%CI 1.03-1.23, p 0.01) and phosphate (aHR 1.35, 95%CI 1.00-1.84, p 0.05), but not calcium (aHR 1.11, 95%CI 0.57-2.17, p 0.76), were associated with all-cause mortality. Calcium was not independently associated with mortality, but modified the effect of phosphate, with the highest mortality risk found in patients with both hypercalcemia and hyperphosphatemia. PTH level was associated with CV mortality, but not with non-CV mortality, whereas phosphate was associated with both CV and non-CV mortality in most models. Conclusions: CKD-MBD is very common in older non-dialysis patients with advanced CKD. PTH and phosphate are independently associated with all-cause mortality in this population. While PTH level is only associated with CV mortality, phosphate seems to be associated with both CV and non-CV mortality.