Association of low serum aluminum level with mortality in hemodialysis patients

Figures & data

Figure 1 Enrollment and status of all study patients.

Abbreviations: SAL, serum aluminum level; HD, hemodialysis.

Table 1 Baseline characteristics of study patients who had different serum aluminum levels (n=901)

Characteristics	First quartile (SAL <6 μg/L) (n=222)	Second quartile (SAL: 6–9 μg/L) (n=229)	Third quartile (SAL: 9–13 µg/L) (n=230)	Fourth quartile (SAL >13 μg/L) (n=220)	P-value
Demographics
Age (years)	56.0±13.6	55.3±13.9	55.3±13.6	58.4±13.1	0.080
Gender (female)	94 (41.8)	109 (50.4)	119 (52.8)	114 (51.4)	0.058
Body mass index (kg/m^2)	22.1±3.3	22.0±2.8	22.2±3.3	22.3±3.3	0.377
Smoking	45 (20.9)	32 (14.6)	41 (17.4)	38 (17.9)	0.623
Comorbidities
Previous CVDs	12 (5.3)	14 (6.2)	11 (4.7)	6 (2.8)	0.111
Hypertension	86 (38.7)	89 (40.3)	78 (33.6)	97 (44.5)	0.539
Diabetes mellitus	52 (23.1)	44 (19.9)	47 (20.4)	56 (24.8)	0.621
Dialysis-related data
HD duration (years)	5.7±4.8	6.4±5.2	6.9±5.3	7.4±5.6	0.001
Use of fistula	182 (82.2)	174 (79.2)	187 (81.7)	170 (77.5)	0.313
Use of BCM dialyzers	169 (76.0)	154 (70.8)	170 (74.0)	162 (73.9)	0.769
Erythropoietin use	210 (94.7)	199 (91.2)	213 (92.8)	200 (89.9)	0.243
Calcitriol use	13 (6.2)	17 (8.0)	38 (17.0)	50 (22.9)	<0.001
Erythropoietin (U/kg/wk)	76.7±44.7	71.3±49.2	73.2±46.4	76.7±45.4	0.909
Kt/V (Daugirdas) urea	1.75±0.33	1.81±0.31	1.83±0.32	1.81±0.33	0.143
nPCR (g/kg/d)	1.16±0.26	1.17±0.26	1.19±0.26	1.19±0.28	0.231
Residual daily urine >100 mL/d	55 (25.3)	40 (17.7)	52 (23.0)	45 (20.6)	0.542
Biochemical data
Hemoglobin (g/dL)	10.5±1.1	10.7±1.5	10.5±1.4	10.4±1.3	0.159
Albumin (g/dL)	4.11±0.33	4.07±0.35	4.08±0.35	4.02±0.37	0.021
Creatinine (mg/dL)	11.1±2.4	11.0±2.4	10.9±2.4	10.4±2.2	0.008
Transferrin saturation (%)	29.7±11.0	30.2±13.7	28.5±12.1	29.5±11.2	0.540
Ferritin (µg/L)	318.4 (8.7–1,454.6)	300.0 (10.9–3,571.2)	299.1 (9.3–4,658.8)	323.5 (6.6–1,641.8)	0.467
Corrected-calcium (mg/dL)	9.7±0.8	9.9±0.9	9.8±0.9	9.9±1.0	0.263
Phosphate (mg/dL)	4.8±1.4	4.8±1.3	4.8±1.4	4.5±1.3	0.020
iPTH (pg/mL)	138.4 (0.20–1,473.7)	109.4 (0.20–1,754.0)	105.1 (0.3–1,655.4)	127.0 (0.7–1,574.2)	0.858
Cardiovascular risks
HDL-C (mg/dL)	43.6±14.3	46.0±13.6	45.0±14.3	45.5±16.4	0.285
LDL-C (mg/dL)	93.5±29.7	98.7±29.6	95.2±29.9	92.4±31.5	0.458
hsCRP (mg/L)	2.62 (0.20–63.45)	3.01 (0.32–70.88)	2.70 (0.20–49.40)	3.13 (0.21–73.21)	0.668
Cardiothoracic ratio (%)	49.8±6.9	49.6±6.7	49.6±7.4	50.1±6.8	0.626

Notes: Data are presented as means ± SDs, numbers (percentages), or medians (minimum, maximum). Significance was assessed by ANOVA test or Chi-square test. A P-value of <0.05 was considered statistically significant. Previous CVD includes cerebrovascular disease, coronary arterial disease, congestive heart failure, or peripheral vascular disease. Hypertension was defined as; blood pressure ≥140/90 mmHg based on at least two measurements or regular use of an antihypertensive drug. Diabetes mellitus was diagnosed by a physician previously or by two measurements of fasting glucose of 126 mg/dL or more.

Abbreviations: BCM, biocompatible membrane; CVD, cardiovascular disease; HD, hemodialysis; HDL, high-density lipoprotein; hsCRP, high sensitivity C-reactive protein; iPTH, intact parathyroid hormone; LDL, low-density lipoprotein; nPCR, normalized protein catabolic rate; SAL, serum aluminum level; SD, standard deviation.

Table 2 Factors associated with log₁₀ (SAL) in study patients (n=901)

Variable	Simple linear regression analysis (β coefficient ± SE)	P-value	Multiple linear regression analysis (β coefficient ± SE)	P-value
HD duration (years)	0.006±0.002	0.002	0.004±0.002	0.033
Hypertension (Yes =1)	0.082±0.029	0.005	–	–
Calcitriol use (Yes =1)	0.160±0.032	<0.001	0.154±0.032	<0.001
Kt/V (Daugirdas)	0.077±0.034	0.023	–	–
Albumin (g/dL)	−0.072±0.031	0.021	–	–
Creatinine (mg/dL)	−0.01±0.005	0.017	–	–
Phosphate (mg/dL)	−0.023±0.008	0.004	−0.026±0.008	–

Abbreviations: Log, logarithmic transformation; SAL, serum aluminum level; SE, standard error; HD, hemodialysis.

Figure 2 Kaplan–Meier survival curves of the different SAL quartiles.

Abbreviations: Cum, cumulative; SAL, serum aluminum level.

Table 3 Multivariate Cox regression analysis of 12-month mortality in study patients (n=901) according to baseline quartile of SAL and variables with P-values less than 0.05 in univariate Cox analysis

Variable	Multivariate HR (95% CI)	P-value
Age (years) (increment of 1 year)	1.05 (1.02–1.08)	0.003
Hemoglobin (g/dL) (increment of 1 g/dL)	0.74 (0.58–0.94)	0.012
Log hsCRP (mg/L) (increment of 10 mg/mL)	2.51 (1.34–4.70)	0.004
First quartile SAL as reference (HR =1)
Second quartile SAL	2.46 (0.45–13.33)	0.462
Third quartile SAL	1.31 (1.12–1.53)	0.038
Fourth quartile SAL	3.19 (1.08–8.62)	0.048

Abbreviations: HR, hazard ratio; CI, confidence interval; hsCRP, high sensitivity C-reactive protein; SAL, serum aluminum levels.