Sodium Restriction May Not Benefit All Patients With Heart Failure

A new review from investigators at Soochow University in China of 10 randomized controlled trials (RCTs) published through December 20, 2020, shows that despite imposing limits on dietary sodium intake (> 3000 mg) among patients with heart failure, few actually benefit from the lifestyle recommendation. Outcomes were evaluated over both the short term (30 days or fewer) and the long term (more than 30 days) and compared with a control group.

For the 3 outcomes of quality of life (QOL; the primary study outcome) and mortality and hospital readmission risks (secondary study outcomes), improvements were not seen among the 1011 patients covered in the 10 trials found through a search of PubMed, the Cochrane Central Register of Controlled Trials, EMBASE, and Cumulative Index to Nursing and Allied Health. Follow-up among patients ranged from 7 days to almost 7 years.

The study was published recently in The Journal of Cardiovascular Nursing.

“The literature is still limited regarding the effect of dietary salt restriction on QOL in patients with heart failure,” the authors wrote. “We performed a systematic review and metal-analysis, including RCTs with sodium restriction as an intervention.”

Overall for the study group, there was a nonsignificant reduction in QOL (standardized mean difference [SMD] –0.17p; 95% CI, ­–0.64 to 0.30; P = .47), with the authors highlighting significant heterogeneity (P_{heterogeneity} = .003; I² = 75%).

However, when looking at outcomes based on follow-up time of 30 days or less, there was actually a reduction in QOL seen among the sodium-restricted group (SMD, –1.16; 95% CI, –1.76 to –0.56; P_random = .0002). In addition, for follow-up times of 30 days or more, no difference in QOL was seen following sodium restriction (SMD, 0.06; 95% CI, –0.18 to 0.31; P_random = .61).

A random-effects meta-analysis further demonstrated an 84% greater mortality risk among patients with heart failure instructed to reduce their sodium (relative risk [RR], 1.84; 95% CI, 1.52-2.23; P_random < .00001). “This pooled analysis,” the authors noted, “yielded high homogeneity, with an I2 statistic of 0% (P_{heterogeneity} = .65).”

There was also a higher risk of hospital readmission seen among the restricted group (RR, 1.61; 95% CI, 1.20-2.15), and this result had significant heterogeneity (P_{heterogeneity} = .01; I² = 65%). For this outcome, based on follow-up of greater than 30 days, there was a 73% greater hospital readmission risk seen among the restricted group (RR, 1.73; 95% CI, 1.28-2.33; P_random = .0003). Significant difference between the sodium-restricted and control groups were not seen when considering 30 days or less of follow-up.

The authors noted that the benefits of a low-sodium diet are now being challenged, despite several national and international guidelines recommending such diets to reduce congestion among patients with heart failure. In fact, their findings, they add, do not support such a dietary intervention.

When clarifying why low-sodium diets may not be beneficial after all, the authors cited reasons that include low sodium–induced hyponatremia, activation of antidiuretic and antinatriuretic systems, poor appetite, low caloric intake, and malnutrition. It’s also possible for there to be interactions between malnutrition, inflammation, and oxidative stress, which can adversely affect the progression of heart failure.

The authors stress the importance of considering patient QOL in light of clinical improvements. “QOL is often overlooked by clinicians because it cannot reflect more objective indicators of health status,” they wrote. “As a consequence, QOL often does not change even when clinicians have determined that a patient’s condition may have improved.”

Their recommendation is for a relaxation of sodium-restriction guidelines among patients with heart failure and for these dietary interventions to be explored after evaluation of New York Heart Association functional class and American Heart Association stage, “which may reduce the suffering of patients from adherence to sodium restriction and even allow them to have a better QOL.”

Reference

Zhu C, Cheng M, Su Y, Ma T, Lei X, Hou Y. Effect of dietary sodium restriction on the quality of life of patients with heart failure: a systematic review of randomized controlled trials. J Cardiovasc Nurs. Published online December 23, 2021. doi:10.1097/JCN.0000000000000880