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12th April 2022
A randomised trial by researchers from the Canadian VIGOUR Centre, University of Alberta, Canada showed that reduced sodium intake had no effect on clinical events including cardiovascular-related hospitalisations or mortality in ambulatory heart failure patients compared with usual care, but did have a small, but significant, positive effect on quality of life and improved disease functional class.
In patients with congestive heart failure, the reduced low cardiac output decreases the fullness of the arterial circulation initiates several internal mechanisms to increase vascular resistance and enhance sodium and water renal retention. In fact, in a study that examined factors associated with a worsening of heart failure, noncompliance with salt restriction, was a factor in over a fifth (22%) of cases.
As a result, dietary advice advocating a reduced sodium intake is arguably the most frequent self-care behaviour recommendation to patients with heart failure and is endorsed by all heart failure guidelines. Currently, the American Heart Association recommends a reduction of sodium intake to <2300 mg/d for general cardiovascular health promotion but notes how there are no trials to support this level of restriction in patients with heart failure.
Nevertheless, the beneficial effect of lowering sodium intake is not clear cut and some evidence suggests that a reduced sodium intake to less than 2g/day is unwarranted in mild heart failure. In contrast, other data shows that sodium restriction (< 2.5 g/day) was associated with a significantly higher risk of death or heart failure hospitalisation.
With some uncertainties over whether a reduced sodium intake was beneficial to those with heart failure, for the present study, the Canadian team examined the effect of a dietary intervention of less than 1.5 g/day (1500 mg) of sodium compared to usual care, i.e., where no such recommendation was in place. Included patients had chronic heart failure (New York Heart Association functional class, 2 – 3) and had optimal medical therapy. Individuals were then randomised 1:1 to the low sodium diet or usual care. The low sodium intervention was supported by behavioural counselling and meal plans and menus for a period of 12 months. Dietary sodium intake was assessed using a 3-day food record at baseline and again after 6 and 12 months for both groups. The primary outcome of interest was a composite of cardiovascular-related hospitalisation, cardiovascular-related emergency department visits and all-cause mortality within 12 months of randomisation. In addition, to the clinical outcomes, quality of life was assessed using the Kansas City Cardiomyopathy Questionnaire (KCCQ) overall summary score, as well any changes in the New York Heart Association functional class.
Reduced sodium intake and cardiovascular outcomes
A total of 806 patients with median age of 67 years (66% male) were randomised to the low sodium arm (397) or usual care. At baseline the median sodium intake was 2286 mg/day for the low sodium group and 2119 mg/day for control arm. After 12 months, the sodium intake reduced by 4% in the control arm but by 28% in the low sodium group.
Within 12 months, the primary outcome occurred in 15% of those in the low sodium arm and 17% in the usual care group (adjusted hazard ratio, HR = 0.99, 95% CI 0.66 – 1.47, p = 0.95). All-cause mortality rates were also similar (6% vs 4%, low sodium vs usual care), giving a hazard ratio of 1.35 (95% CI 0.64 – 2.82, p = 0.43).
Whilst there were no significant differences in clinical outcomes, participants assigned to the low sodium group did see a small, but significant increase in the overall KCCQ summary score of 3.38 points (p = 0.011) and those in the low sodium group had a greater odds of improving by one NYHA functional class compared to the usual care group (odds ratio, OR = 0.59, 95% CI 0.40 – 0.86, p = 0.006).
The authors concluded that while a low sodium diet did not impact significantly on clinical outcomes, it did produce small but significant improvements in quality of life and NYHA functional class.
Ezekowitz JA et al. Reduction of dietary sodium to less than 100 mmol in heart failure (SODIUM-HF): an international, open-label, randomised, controlled trial Lancet 2022