Sodium Intake and its association with Mortality in Chronic Kidney Disease patients

Abstract

Background & Aims: Current guidelines advise sodium restriction in all patients with chronic kidney disease (CKD). However, there is no direct evidence linking sodium intake to increased mortality. This study aims to investigate the relationship between sodium intake and mortality in CKD patients. Methods: A retrospective cohort analysis, using routine clinical data from electronic healthcare records. Sodium intake was estimated by 24-hour urinary sodium excretion. Patients with a GFR of 15 to 60, with at least one 24-hour sodium excretion, visiting an outpatient clinic for dietetics and cardiovascular risk management were included. The association between sodium intake and mortality was investigated in two manners: 1) sodium intake as a continuous determinant; 2) sodium intake categorized as: low (i.e. < 100 mmol/day), middle (i.e. 100-200 mmol/day), and high (i.e. >200 mmol/day) intake. Cox proportional hazard analysis, adjusted for patient characteristics, kidney function and cardiovascular risk factors, was used to calculate hazard ratios time-varying sodium intake. Results: In total, 3787 patients were included. 1268 patients were low-intake, 1966patients were mid-intake, 553 patients were high intake. Less than 33.5% of patients had a sodium intake below 100 mmol (equivalent to 5 grams of salt) per day. In the low sodium intake group, 38% of patients died, versus 22.1% in the high intake group. The corrected hazard ratios for mortality were 0.63 (95% CI: 0.55 – 0.72) for medium sodium intake and 0.68 (95% CI: 0.55 – 0.83) for high sodium intake. This hazard ratio accounts for varying levels of sodium intake over time. Conclusions Very low sodium intake is correlated with mortality, irrespective of kidney function. Furthermore, adherence to sodium guidelines is not possible for most patients. Sodium restriction should not be prescribed to all CKD patients. Rather, a personalised approach should be taken by doctors, dieticians, and patients.