Effects of salt substitutes on clinical outcomes: a systematic review and meta-analysis. Issue 20 (9th August 2022) - Yin, Xuejun
Abstract : Objectives: The Salt Substitute and Stroke Study (SSaSS) recently reported blood pressure-mediated benefits of a potassium-enriched salt substitute on cardiovascular outcomes and death. This study assessed the effects of salt substitutes on a breadth of outcomes to quantify the consistency of the findings and understand the likely generalisability of the SSaSS results. Methods: We searched PubMed, Embase and the Cochrane Library up to 31 August 2021. Parallel group, step-wedge or cluster randomised controlled trials reporting the effect of salt substitute on blood pressure or clinical outcomes were included. Meta-analyses and metaregressions were used to define the consistency of findings across trials, geographies and patient groups. Results: There were 21 trials and 31 949 participants included, with 19 reporting effects on blood pressure and 5 reporting effects on clinical outcomes. Overall reduction of systolic blood pressure (SBP) was −4.61 mm Hg (95% CI −6.07 to −3.14) and of diastolic blood pressure (DBP) was −1.61 mm Hg (95% CI −2.42 to −0.79). Reductions in blood pressure appeared to be consistent across geographical regions and population subgroups defined by age, sex, history of hypertension, body mass index, baseline blood pressure, baseline 24-hour urinary sodium and baseline 24-hour urinary potassium (all p homogeneity >0.05). Metaregression showed that each 10% lower proportion of sodium choloride in the salt substitute was associated with a −1.53 mm Hg (95% CI −3.02 to −0.03, p=0.045) greater reduction in SBP and a −0.95 mm Hg (95% CI −1.78 to −0.12, p=0.025) greater reduction in DBP. There were clear protective effects of salt substitute on total mortality (risk ratio (RR) 0.89, 95% CI 0.85 to 0.94), cardiovascular mortality (RR 0.87, 95% CI 0. 81 to 0.94) and cardiovascular events (RR 0.89, 95% CI 0.85 to 0.94). Conclusions: The beneficial effects of salt substitutes on blood pressure across geographies and populations were consistent. Blood pressure-mediated protective effects on clinical outcomes are likely to be generalisable across population subgroups and to countries worldwide. Trial registration number: CRD42020161077.