The baseline characteristics of the patients are depicted in Table 1. A total of 125 hemodialysis patients were included in this observational study, of whom 59.2% were males and 40.8% were females, with an average age of 56.22 ± 12.64 years old. The median dialysis vintage was 4 years (rang of 2–10 years). The etiology of end-stage renal disease (ESRD) for the study population was Chronic glomerulonephritis (67.2%), diabetic nephropathy (17.6%), polycystic kidney disease (6.4%), Benign hypertensive nephrosclerosis (3.2%), IgA nephropathy (2.4%), medullary sponge kidney (1.6%),ectopic kidney (0.8%) and Anca-associated vasculitis (0.8%). No significant differences were noted in sex, dialysis vintage, comorbidity, spKT/V, etiology, Hb, albumin, calcium, phosphate, parathyroid hormone, hs-CRP, age, except for β2-microglobulin levels, between two groups. BMI and β2-microglobulin levels were higher in SPDDS group (P = 0.025 for BMI; P = 0.039 for β2-MG) (Table 1).

Baseline hs-CRP was 3.30 (1.04, 5.05) mg/l in the CDDS group and 2.40 (1.02, 5.00) mg/l in the SPDDS group. hs-CRP levels decreased significantly in CDDS patients and increased significantly on SPDDS groups over time (all P < 0.05) (Table 2 and Fig. 1).

The median value of hs-CRP, ALB, and β2-microglobulin for both groups during the follow-up period. A hs-CRP throughout the follow-up period. B ALB throughout the follow-up period. C β2-microglobulin throughout the follow-up period

A GLMM analysis was described in Table 3. The GLMM analysis was conducted taking into account the three factors including times (baseline, 3 months later, and final observation), group (CDDS and SPDDS groups), and the interaction between time and group, with confounding factors such as sex, age, dialysis vintage, and BMI as fixed effects and individual as a random effect. In the GLMM analysis, SPDDS group were used as reference group. As Table 3 shown, there was a significant time*group interaction effect on hs-CRP changes over the follow-up period (β = -1.966, FTime* CDDS group = 13.389, P < 0.001), indicating that for every unit increase in time, the CDDS group showed a significantly decrease in hs-CRP level compared to the SPDDS group (an additional decrease of 1.966) (Table 3 and Fig. 1).

Additionaly, In GLMM analysis adjusted for various confounders, patients with older age, and higher BMI were significantly associated with higher hs-CRP(age: β = 0.079, P < 0.001; BMI: β = 0.160, P = 0.003).

In linear mixed model analysis which used random slope model, group factor was used as random effects, and time factor as fixed effects. A different slope was observed between CDDS group and SPDDS group (βCDDS =—0.793; βSPDDS = 0.791), indicating that a decreased hs-CRP levels in CDDS group, while increased in the SPDDS group over the follow-up period (Fig. 2).

Trajectory Plot of Two Groups by Linear Mixed Models with Random Slopes

Baseline albumin was 38.3 (35.4, 39.8) mg/l in the CDDS group and 38.3 (36.3, 40.4) mg/l in the SPDDS group. No significant differences were found between the two groups(all P > 0.05) (Table 1).

In GLMM analysis adjusted for various confounders, patients with older age and shorter dialysis vintage were significantly associated with lower albumin (age: β =—0.003, P < 0.001; dialysis vintage: β = 0.004, P = 0.008) (Table 3). However, no significant time*group interaction effect was observed on ALB level changes over the follow-up period (β = 0.012, FTime* CDDS group = 1.429, P = 0.233), which suggested that there was no significant difference in the fluctuation of ALB levels between the CDDS and SPDSS group over time during the follow-up period (Fig. 1).

Baseline β2—microglobulin was 19.90 (17.66, 21.63) mg/dl in the CDDS group and 21.30 (18.44, 25.28) mg/dl in the SPDDS group. No significant differences were noted over time in the two groups (all P > 0.05) (Table 2).

In GLMM analysis adjusted for various confounders, female, patients with longer dialysis vintage, and lower BMI significantly were associated with higher β2—microglobulin level(male: β = -1.406, P = 0.019; dialysis vintage: β = 0.159, P = 0.023; BMI: β = -0.235, P < 0.001) (Table 3). However, no significant time*group interaction effect was observed on β2-MG level changes over the follow-up period (β = -0.658, FTime* CDDS group = 1.228, P = 0.269), demonstrated a similar changes of β2-MG levels between the CDDS and SPDSS group over time during the follow-up period (Fig. 1).