Sodium excretion linked to CVD risk in chronic kidney disease

By Laura Cowen

High levels of sodium excretion are associated with a significantly increased risk of cardiovascular disease (CVD) in patients with chronic kidney disease (CKD), US study findings indicate.

The results of the prospective cohort study were independent of several important CVD risk factors, including use of antihypertensive medication, baseline estimated glomerular filtration rate (eGFR) and history of CVD.

"These findings, if confirmed by clinical trials, suggest that moderate sodium reduction among patients with CKD and high sodium intake may lower CVD risk", say Jiang He (Tulane University, New Orleans, Louisiana) and co-researchers.

During a median follow-up of 6.8 years, 804 composite CVD events (comprising 575 cases of heart failure, 305 myocardial infarctions and 148 strokes) occurred in 3757 participants (mean age 58 years; 45% women) of the multicenter Chronic Renal Insufficiency Cohort Study.

The cumulative incidence of composite CVD events increased with increasing levels of urinary sodium excretion, based on a cumulative average from samples collected over a 24-hour period at baseline and the first two annual follow-up visits and calibrated to gender-specific mean 24-hour urinary creatinine excretion.

Specifically, the cumulative composite CVD incidence was 18.4% among patients in the lowest quartile of calibrated sodium excretion (<2894 mg/24 hours), 16.5% among those in the second quartile (2894-3649 mg/24 hours), 20.6% among those in the third quartile (3650-4547 mg/24 hours) and 29.8% in the highest quartile (≥4548 mg/24 hours).

Multivariate analyses showed that the risk of composite CVD events was a significant 1.36-fold higher for participants in the highest quartile of calibrated sodium excretion compared with those in the lowest quartile.

In addition, the risks for heart failure and stroke were a significant 1.34- and 1.81-fold higher for those in the lowest versus highest quartiles, but there was no significant association for myocardial infarction.

He and team note in JAMA that previous studies have reported a J- or U-shaped association between dietary sodium and CVD. This analysis, however, showed no significant evidence of a nonlinear association and indicated that there was, in fact, a significant linear association. The researchers say that this discrepancy could be due to "methodologic limitations" of earlier studies.

In an accompanying editorial, Neil Powe and Kirsten Bibbins-Domingo, from the University of California in San Francisco, USA, comment: "This is a call for awareness of the results of this important study".

They say: "If the results reported [...] are validated in experimental studies, efforts to influence sodium intake in persons with CKD could save many lives and medical costs."

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