Salt substitution and salt-supply restriction for lowering blood pressure in elderly care facilities: a cluster-randomized trial

There is a paucity of high-quality evidence on the effectiveness and safety of salt reduction strategies, particularly for older people, who have the most to benefit but are at higher risk of adverse effects. Here, we conducted a clinical trial in which 48 residential elderly care facilities in China (1,612 participants including 1,230 men and 382 women, 55 years or older) were cluster-randomized using a 2 × 2 factorial design to provision of salt substitute (62.5% NaCl and 25% KCl) versus usual salt and to a progressively restricted versus usual supply of salt or salt substitute for 2 years. Salt substitute compared with usual salt lowered systolic blood pressure (-7.1 mmHg, 95% confidence interval (CI) -10.5 to -3.8), meeting the primary outcome of the trial, whereas restricted supply compared with usual supply of salt or salt substitute had no effect on systolic blood pressure. Salt substitute also lowered diastolic blood pressure (-1.9 mmHg, 95% CI -3.6 to -0.2) and resulted in fewer cardiovascular events (hazard ratio (HR) 0.60, 95% CI 0.38-0.96), but had no effect on total mortality (HR 0.84, 95% CI 0.63-1.13). From a safety standpoint, salt substitute increased mean serum potassium and led to more frequent biochemical hyperkalemia, but was not associated with adverse clinical outcomes. In contrast, salt restriction had no effect on any study outcome. The results of this trial indicate that use of salt substitute, but not efforts to restrict salt supply, may achieve blood pressure lowering and deliver health benefits to residents of elderly care facilities in China. Clinicaltrials.gov registration: NCT03290716.