Association between the risk of death and serum calcium, phosphate, and intact parathyroid hormone levels in older patients undergoing maintenance hemodialysis: a cohort study in Beijing

BACKGROUND: The number of patients ⩾65 years who require maintenance hemodialysis (MHD) is increasing. Although reduced bone turnover in older patients receiving hemodialysis, as reflected by lower serum intact parathyroid hormone (iPTH) and phosphate (P) levels, has been reported, focus on the association between abnormal bone metabolism and the risk of death in older patients receiving MHD has been limited. METHODS: We retrospectively examined data from the Beijing Hemodialysis Quality Control and Improvement Center for 1410 older patients who underwent hemodialysis from 1 January 2012 to 31 December 2016. Baseline, time-dependent (TD) Cox proportional hazards models and Kaplan–Meier analyses were used to evaluate the association between the markers of mineral and bone disorder (MBD) [calcium (Ca), P, and iPTH] and survival. The Kidney Disease: Improving Global Outcomes (KDIGO) target ranges were included as reference values. RESULTS: Serum P levels >2.49 mmol/l increased the risk of all-cause death [hazard ratio (HR): 1.46; 95% confidence interval (CI): 1.04–2.07; p = 0.030] and cardiovascular death (HR: 2.01; 95%CI: 1.21–3.34; p = 0.007); iPTH levels >600 pg/ml increased the risk of cardiovascular death (HR: 1.95; 95%CI: 1.20–3.15; p = 0.007). Baseline results and TD Cox analyses were similar. All three MBD parameters were within the respective target ranges at least once during the follow-up period in 399 (28.3%) patients, and these patients had better survival rates than those who achieved two of the three target ranges (715/1410 patients; 50.7%); those who achieved one or no target range (296/1410; 21.0%) had the lowest survival rate (all-cause death: log-rank chi square = 83.96, p < 0.001; cardiovascular death: log-rank chi square = 47.06, p < 0.001). CONCLUSION: Older patients undergoing MHD who achieved the KDIGO target levels for any two or three MBD parameters had lower risks of all-cause and cardiovascular death.