The impact of low serum sodium level on mortality depends on glycemic control
Osman Z Sahin1, Gulay Asci, Fatih Kircelli
1Division of Nephrology, Ataturk Traning and Research Hospital, Izmir, Turkey. drosahin@yahoo.com
Insights
Low serum sodium levels increase mortality risk in hemodialysis patients, particularly those with diabetes. This association appears linked to poor glycemic control, highlighting the importance of managing blood sugar.
Area of Science:
- Nephrology
- Endocrinology
- Clinical Medicine
Background:
- Low serum sodium (hyponatremia) is linked to increased mortality in chronic kidney disease (CKD) patients.
- The relationship between serum sodium and mortality in hemodialysis (HD) patients, especially concerning glycemic control, requires further investigation.
Purpose of the Study:
- To examine the association between serum sodium levels and mortality in hemodialysis patients.
- To investigate the role of glycemic control in this association.
Main Methods:
- Prospective observational study of 697 prevalent hemodialysis patients.
- Follow-up for all-cause and cardiovascular mortality.
- Statistical analysis using Cox regression models.
Main Results:
- Low serum sodium concentration (<135 mEq/L) was present in 5.9% of patients.
- The lowest quartile of serum sodium was associated with a 2.13-fold increased risk of overall mortality.
- Each 1 mEq/L increase in serum sodium was linked to reduced overall and cardiovascular mortality risk (HR 0.87 and 0.86, respectively).
- This association was significant in diabetic patients but not in non-diabetics.
- The survival benefit of higher serum sodium in diabetics was lost after adjusting for HbA1c levels.
Conclusions:
- Low serum sodium concentration is associated with increased mortality risk, but only in hemodialysis patients with diabetes.
- The impact of serum sodium on survival in diabetic hemodialysis patients appears to be mediated by poor glucose control (elevated HbA1c).
Background:
Low serum sodium levels have been associated with mortality both in patients with and without chronic kidney disease. In this study, we investigated this association in relation to glycemic control in hemodialysis (HD) patients.
Materials And Methods:
Between March and September 2005, 697 prevalent HD patients were enrolled in this prospective observational study and followed up for all-cause and cardiovascular mortality. The associations of serum sodium concentration with both overall and cardiovascular survival rates were studied.
Results:
At baseline, mean predialysis serum sodium concentration was 138.4 ± 2.3 mEq/L (range: 130-145 mEq/L). Mild hyponatremia (< 135 mEq/L) was present in only 41 subjects (5.9%), and no patient had serum sodium level < 130 mEq/L. During 20.2 ± 6.2 months of follow-up, 119 patients (15.9%) died, 68 from CV causes. In adjusted Cox regression analysis, lowest sodium quartile was associated with 2.13-fold increased risk of overall mortality (95% confidence interval (CI) 1.14-3.98, P = 0.01, model chi-square 114.6, P < 0.001). As a continuous variable, each 1 mEq/L increase in predialysis sodium concentration was associated with a hazard ratio (HR) of 0.87 for overall mortality (95% CI 0.81-0.95, P = 0.002) and 0.86 for cardiovascular mortality (95% CI 0.78-0.96, P = 0.007). The predictivity of low serum sodium was prominent in diabetic subjects but not in nondiabetics. However, relationship between serum sodium and patient survival in diabetics was lost after adjustment for the HbA1c level: HR 0.91 (95% CI 0.78-1.05, P = 0.20).
Conclusions:
Low serum sodium concentration is associated with mortality only in those with diabetes. Furthermore, the impact of serum sodium on survival in these patients seems to be derived from poor glucose control.
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