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, χ²=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.