Salt substitute use not salt reduction key to BP lowering and CVD prevention in elderly: DECIDE trial

The study, published in Nature Medicine, showed clear benefits of salt substitute versus usual salt for BP lowering and protection against cardiovascular events in people living in residential elderly care facilities in China. An increase in the frequency of biochemical hyperkalemia was also found without adverse clinical outcomes.

"Efforts to restrict the supply of salt did not achieve the target for BP lowering planned in our study,' the researchers wrote. This requires further analysis to understand this intervention's implementation and feasibility better.

High BP is the leading cause of death, and previous studies have shown that increasing dietary potassium intake and lowering dietary sodium intake can reduce blood pressure. In China, sodium consumption is high, and salt substitution is a proven nonpharmaceutical intervention for lowering blood pressure. There have been few studies of salt substitutes among older populations at the most significant risk and who have the most benefit. There have also been concerns about hyperkalemia risk, but safety data are limited.

Against the above background, Yifang Yuan, Peking University First Hospital, Beijing, China, and colleagues aimed to use a factorial design to find out the safety and effectiveness of two scalable and practical sodium reduction intervention strategies in parallel, targeting elderly collectively living in residential elderly care facilities: (1) replacement of usual salt with salt substitute and (2) making a stepwise reduction in the salt quantity/salt substitute supplied to facility kitchens.

They conducted a clinical trial in which 48 residential elderly care facilities in China with 1,612 participants (55 years or older) were cluster-randomized using a design of 2 × 2 factorial to the provision of salt substitute (62.5% NaCl and 25% KCl) versus usual salt and to a progressively restricted versus usual salt supply or salt substitute for two years.

The researchers reported the following findings:

• Compared with usual salt, salt lowered systolic blood pressure (–7.1 mmHg), meeting the trial's primary outcome. In contrast, restricted supply compared with the usual salt or salt substitute did not affect systolic blood pressure.
• The salt substitute also lowered diastolic blood pressure (–1.9 mmHg) and led to fewer cardiovascular events (hazard ratio (HR) 0.60) but did not affect total mortality (HR 0.84).
• From a safety standpoint, salt substitute raised mean serum potassium and resulted in more frequent biochemical hyperkalemia but was not tied to adverse clinical outcomes. In contrast, salt restriction did not affect any study outcome.

The studies consistently and strongly support the more widespread use of salt substitutes to prevent cardiovascular disease (CVD). However, efforts to restrict salt supply were unsuccessful, with no detectable effect on blood pressure during the two years of intervention and no benefit for cardiovascular outcomes observed.

"The trial's results indicate that the use of salt substitutes, but not efforts to restrict salt supply, may achieve BP reduction and deliver health benefits to residents of China's elderly care facilities," the researchers conclude.

Reference:

Yuan, Y., Jin, A., Neal, B. et al. Salt substitution and salt-supply restriction for lowering blood pressure in elderly care facilities: a cluster-randomized trial. Nat Med 29, 973–981 (2023). https://doi.org/10.1038/s41591-023-02286-8