Association of low serum aluminum level with mortality in hemodialysis patients

BACKGROUND: The National Kidney Foundation–Kidney Disease Outcomes Quality Initiative recommends that the serum aluminum level (SAL) should be below 20 µg/L for patients with maintenance hemodialysis (MHD). However, serum aluminum may have toxic effects on MHD patients even when it is in the apparently acceptable range (below 20 µg/L). METHODS: The Medical Ethics Committee approved this study. Initially, 954 MHD patients in dialysis centers were recruited. A total of 901 patients met the inclusion criteria and were followed-up for 1 year. Patients were stratified by SAL into four equal-sized groups: first quartile (<6 µg/L), second quartile (6–9 µg/L), third quartile (9–13 µg/L), and fourth quartile (>13 µg/L). Demographic, biochemical, and dialysis-related data were obtained for analyses. A linear regression model was applied to identify factors associated with SAL. Cox proportional hazard model was used to determine the significance of variables in prediction of mortality. RESULTS: Only 9.3% of MHD patients had SALs of 20 µg/L or more. At the end of the follow-up, 54 patients (6%) died, and the main cause of death was cardiovascular disease. Kaplan–Meier survival analysis showed that patients in the fourth SAL quartile had higher mortality than those in the first SAL quartile (log rank test, χ(2)=13.47, P=0.004). Using the first quartile as reference, Cox multivariate analysis indicated that patients in the third quartile (hazard ratio =1.31, 95% confidence interval =1.12–1.53, P=0.038) and the fourth quartile (hazard ratio =3.19, 95% confidence interval =1.08–8.62, P=0.048) had increased risk of all-cause mortality. CONCLUSION: This study demonstrates that SAL, even when in an apparently acceptable range (below 20 µg/L), is associated with increased mortality in MHD patients. The findings suggest that avoiding exposure of aluminum as much as possible is warranted for MHD patients.