Association between time-varying serum lipid levels and all-cause mortality in haemodialysis and peritoneal dialysis patients

Abstract

Objective: Changes in lipid levels over time and the associated all-cause mortality have not yet been studied in different populations of patients undergoing dialysis. This study aimed to investigate the differences in time-varying serum lipid levels and all-cause mortality among haemodialysis (HD) and peritoneal dialysis (PD) patients over a 5-year follow-up period.

Methods: This observational study included Chinese patients with end-stage renal disease (ESRD) who started HD or PD at Sun Yat-sen Memorial Hospital from January 2010 to February 2018. Changes in lipid profiles and trends of change in overall survival rates between the two groups were investigated. Risk factors for the outcome were identified, and the optimal cut-off values were determined using ROC analysis. Additionally, the relationship between the group variable and the outcome measure was assessed using linear regression with a generalized estimating equation (GEE) model.

Results: A total of 141 patients (74 HD patients and 67 PD patients) were enrolled in the study. Forty-three (30.71%) patients died during the follow-up period. Compared with the HD group, the PD group had significantly greater triglyceride (TG) (Year 1 and Year 2) and low-density lipoprotein cholesterol (LDL-C) (Year 2) levels and significantly lower high-density lipoprotein cholesterol (HDL-C) (Year 1 and Year 2) levels. There was no significant difference in total cholesterol (TC) levels. The GEE results revealed similar changes in lipid levels between HD patients and PD patients over time. The Kaplan‒Meier survival curve revealed that there was no significant difference in overall survival between the two groups (log-rank test, P = 0.119). Furthermore, the multivariate Cox proportional hazard regression models demonstrated that baseline HDL-C levels (HR: 0, 95% CI: 0 to 0.11; P = 0.004) and changes in LDL-C levels from baseline to 3 years of follow-up(difference from 0 to 3 years of follow-up) (HR: 0.21, 95% CI: 0.09 to 0.53; P < 0.001) were associated with a greater risk of death in HD patients. An increase in LDL-C levels (difference from 0 to 3 years of follow-up) ≤ 0.24 mmol/L in HD patients and age ≥ 53 years in all patients initiating dialysis was associated with a significantly increased risk of mortality.

Conclusion: The baseline levels of HDL-C and changes in LDL-C levels over a three-year period were significant predictors of all-cause mortality in HD patients, which differed from the lack of significant risk factors observed in the PD group.

Keywords: Haemodialysis; Lipid; Mortality; Peritoneal dialysis; Time-varying.

Fig. 1

The line chart of index results from year 0 to year 5, including TG (A), TC (B), HDL-C (C), LDL-C (D), UA (E), SOD (F), Ferritin (G), iPTH (H), HB (I) and ALB (J)

Fig. 2

The Kaplan-Meier survival functions of HD and PD groups to overall survival

Fig. 3

The forest plot of all estimated hazard ratio (HR) in multivariate models

Fig. 4

The ROC of independent variables to dead outcome, including all patient’s age and Ca (difference 0 to 3) (A), all patient’s PALB (negative related to dead outcome) (B), HD group’s HDL-C (baseline) and LDL-C (difference 0 to 3) (both negative related to dead outcome) (C), PD group’s PALB (negative related to dead outcome) (D)