Longitudinal association between dietary protein intake and survival in peritoneal dialysis patients

Figures & data

Table 1. Baseline DPI, nutritional parameters and dialysis adequacy of 668 PD patients.

Variables	Data
height, cm	163.60 ± 8.49
body weight, kg	63.42 ± 12.55
BMI	23.58 ± 3.71
Charlson index	6 (4,7)
DPI, g/kg/day	0.86 ± 0.25
DEI, kcal/kg/day	25.45 ± 6.86
Fat intake, g/d	53.23 (43.25, 65.79)
Carbohydrate intake, g/d	195.80 (155.90, 237.76)
Alb, g/l	37.54 ± 4.68
Dialysis dose, ml	6762.38 ± 1765.05
ultrafiltration, ml	360.00 (132.50,650.00)
urine volume, ml	550.00 (250.00,950.00)
total fluid removal, ml	994.50 (700.00,1317.50)
Kt/V	1.99 ± 0.62
Tccr (L/w)	59.16 (47.15, 75.23)
eGFR, ml/min	2.40 (1.11, 3.97)
Nitrogen intake, g/d	8.02 ± 2.48
TNA, g/d (Bergstrom)	9.55 ± 2.08
TNA, g/d (New formula)	8.01 ± 2.14
NB, g/d (Bergstrom)	−1.52 ± 2.65
NB, g/d (New formula)	0.01 ± 2.68
Hb, g/l	115.90 ± 19.43
Serum, creatinine, umol/l	718.07 ± 256.71
Serum urea, mmol/l	20.62 ± 6.00
Serum calcium, mmol/l	2.25 ± 0.29
Serum phosphate, mmol/l	1.52 ± 0.41
Serum potassium, mmol/l	4.30 ± 0.75
Serum sodium, mmol/l	139.20 ± 3.13
CO2CP, mmol/l	26.93 ± 3.71

DPI: dietary protein intake; PD: peritoneal dialysis; BMI: body mass index; DEI: dietary energy intake; Alb: albumin; Tccr: total clearance rate of creatinine; eGFR: estimated Glomerular filtration rate; TNA: total nitrogen appearance; NB: nitrogen balance; Hb: hemoglobin; CO₂CP: carbon dioxide combining power.

Table 2. Univariate and multivariate Cox regression analysis of the impact of baseline data on mortality.

Variables	Hazard ratios	95% CI	p value
univariate Cox regression analysis
Age, years	1.055	1.045–1.066	<0.001
gender, male vs. female	0.965	0.769–1.211	0.761
Charlson index, points	1.419	1.340–1.504	<0.001
DM, yes vs. no	1.796	1.429–2.258	<0.001
DPI, g/kg/day	0.634	0.391–1.029	0.065
DEI, kcal/kg/day	0.963	0.946–0.981	<0.001
Serum creatinine, umol/l	0.998	0.998–0.999	<0.001
Serum urea, mmol/l	0.961	0.941–0.982	<0.001
Serum calcium, mmol/l	0.950	0.646–1.399	0.797
Serum phosphate, mmol/l	0.909	0.678–1.219	0.523
Serum sodium, mmol/l	0.934	0.901–0.969	<0.001
Serum potassium, mmol/l	0.684	0.579–0.809	<0.001
CO2CP, mmol/l	0.994	0.962–1.026	0.711
Alb, g/l	0.923	0.903–0.944	<0.001
Hb, g/l	0.998	0.992–1.004	0.528
N balance, g/d (New formula)	1.032	0.989–1.078	0.149
eGFR, ml/min	1.003	0.956–1.052	0.917
Kt/V	1.029	0.847–1.250	0.775
Multivariate Cox regression analysis^a
Age, years	1.032	1.017–1.046	<0.001
Charlson index, points	1.161	1.059–1.272	0.002
DEI, kcal/kg/day	0.981	0.963–1.001	0.057
Serum sodium, mmol/l	0.960	0.926–0.994	0.022
Serum potassium, mmol/l	0.862	0.730–1.018	0.081
Alb, g/l	0.959	0.933–0.986	0.003

DM: diabetes; DPI: dietary protein intake; DEI: dietary energy intake; CO₂CP: carbon dioxide combining power; Alb: albumin; Hb: hemoglobin; N: nitrogen; eGFR: estimated Glomerular filtration rate.

^aAdjusted for DM, DPI, Serum creatinine, Serum urea.

Figure 1. The Kaplan–Meier survival curves in PD patients according to the baseline DPI level. PD: peritoneal dialysis; DPI: dietary protein intake.

Figure 2. Grouping of time-dependent DPI in PD patients. Red, the consistently median DPI group (0.80–0.99 g/kg/day, n = 253); Green, the consistently low DPI group (0.61–0.79 g/kg/day, n = 154); Blue, the high DPI group (≥1.0 g/kg/day, n = 45). PD: peritoneal dialysis; DPI: dietary protein intake.

Table 3. Baseline characteristics of PD patients according to longitudinal DPI latent classes.

Variables	0.80-0.99g/kg/day n = 253	0.60-0.79 g/kg/day n = 154	≥1.0 g/kg/day n = 45	statistic	p
Age, years	57.6 ± 15.3	58.7 ± 14.8	55.5 ± 16.8	0.796	0.452
BMI, kg/m^2	23.8 ± 3.8	23.7 ± 3.6	23.1 ± 3.4	0.687	0.504
Charlson index, points	5.3 ± 1.9	5.8 ± 2.2	5 ± 2.3	4.846	0.008
DM, n (%)	79 (31.3%)	71 (46.1%)	12 (26.7%)	10.900	0.004
Hb, g/l	116.5 ± 19.3	118.2 ± 18	117.2 ± 15.1	0.408	0.665
Low Alb, n (%)	59 (23.3)	29 (18.8)	11 (24.4)	1.317	0.518
eGFR, ml/min	2.8 ± 2.2	2.9 ± 2.5	4 ± 2.9	4.976	0.007
Tccr, L/w	63.5 ± 20.9	66.1 ± 51.8	72.7 ± 27.7	1.365	0.257
Kt/v	2 ± 0.5	1.9 ± 0.6	2.3 ± 0.7	6.594	0.002
Sodium, mmol/l	139.4 ± 3	139.4 ± 3.2	140.6 ± 2.9	3.353	0.036
Potassium, mmol/l	4.4 ± 0.7	4.4 ± 0.8	4.3 ± 0.7	1.092	0.336
NBs, g/d (New formula)	0.1 ± 2.6	−0.7 ± 2.7	1.1 ± 2.6	10.056	<0.001

PD: peritoneal dialysis; DPI: dietary protein intake; BMI: body mass index; DM: diabetes; Hb: hemoglobin; low Alb: low albumin (<35 g/l); eGFR: estimated glomerular filtration rate; Tccr: total clearance rate of creatinine; NBs: nitrogen balance by new formula; CO₂CP: carbon dioxide combining power.

Table 4. Associations between baseline characteristics and being in latent classes for DPI levels using logistic regression model.

Variables	0.60–0.79 g/kg/day n = 154		≥1.0 g/kg/day n = 45
	OR (95%CI)	p	OR (95%CI)	p
DM	1.488 (0.930,2.380)	0.097	1.054 (0.461,2.410)	0.902
eGFR, ml/min	1.003 (0.895,1.125)	0.957	1.101 (0.934,1.298)	0.251
Kt/v	0.680 (0.418,1.106)	0.120	2.047 (1.006,4.162)	0.048
Na, mmol/l	1.014 (0.947,1.087)	0.687	1.155 (1.027,1.299)	0.016
NBs, g/d	0.857 (0.786,0.933)	<0.001	1.193 (1.055,1.350)	0.005
Charlson index, points	1.142 (1.018,1.281)	0.023	0.893 (0.746,1.068)	0.215

DPI: dietary protein intake; DM: diabetes; Hb: hemoglobin; Alb: Albumin; eGFR: estimated Glomerular filtration rate; Na: serum sodium; K: serum potassium; NBs: nitrogen balance by new formula.

Reference group: 0.80–0.99g/kg/day (n = 253).

Figure 3. The Kaplan-Meier survival curves in PD patients according to the grouping of time-dependent DPI. PD, peritoneal dialysis; DPI, dietary protein intake.

Data availability statement

Data are not available due to the property rights of the healthcare center that has collected these data. Chunyan Su could be contacted if someone wants to request the data.