Salt substitution lowers risk of hypertension in elderly with normal blood pressure
In Chinese older adults with normotension, the use of a potassium-enriched salt substitute instead of regular salt for 2 years reduced the incidence of hypertension by 40%, without increasing the risk of hypotension.
This summary is based on the publication of Zhang X, Yuan Y, Li C, et al. - Effect of a Salt Substitute on Incidence of Hypertension and Hypotension Among Normotensive Adults. J Am Coll Cardiol. 2024 Feb 20;83(7):711-722. doi: 10.1016/j.jacc.2023.12.013
Introduction and methods
Background
Few studies have investigated the blood pressure (BP)–lowering effect of salt substitution in normotensive individuals, and, in addition, their results were contradictory [1-3]. It is also unknown whether the resultant BP lowering increases the risk of hypotension.
Aim of the study
The authors examined the effect of salt substitution on the incidences of hypertension and hypotension among older adults with normal BP.
Methods
This was a post-hoc analysis of the DECIDE-Salt (Diet Exercise and Cardiovascular Health–Salt Reduction Strategies for the Elderly in Nursing Homes in China) trial, a multicenter, 2 × 2 factorial, cluster-randomized trial conducted at 48 elderly care facilities in China [4,5]. In this RCT, 1612 adults aged ≥55 years were cluster-randomized in a 1:1 ratio (stratified by study center) to replacement of usual table salt with a salt substitute (62.5% NaCl, 25% KCl, and 12.5% dried food ingredient flavorings and traces of amino acids) or continuing the use of regular salt for 2 years. Local staff responsible for implementing the intervention was aware of the random assignment, but the outcome assessment team was blinded to the allocation. In this post-hoc analysis, 661 participants with BP <140/90 mmHg who were not on antihypertensive medication at baseline were included (mean age: 71.4 years; mean BP: 121.9/74.4 mmHg; 74.3% male) .
Outcomes
The primary endpoint was incident hypertension, defined as BP ≥140/90 mmHg at ≥2 follow-up visits; initiation of antihypertensive medications; or development of MACE (coronary heart disease or stroke). The secondary safety endpoint was the incidence of hypotensive episodes, defined as clinically diagnosed hypotension; mean arterial pressure<65 mmHg; BP <90/60 mmHg; and/or self-reported hypotension-related symptoms (syncope, dizziness, light-headedness, and blurred vision). Additional secondary endpoints included the mean change in systolic and diastolic BP from baseline.
Main results
- The incidence of hypertension was 11.7 per 100 person-years in participants using the salt substitute (n=313) and 24.3 per 100 person-years in those taking regular salt (n=298) (adjusted HR: 0.60; 95%CI: 0.39–0.92; P=0.02).
- However, the incidence of hypotensive episodes did not differ between the salt-substitute and regular-salt groups (9.0 vs 9.7 per 100 person-years; adjusted rate ratio: 1.10; 95%CI: 0.59–2.07; P=0.76).
- In the salt-substitute group, the mean systolic BP did not change from baseline (–0.3 ± 11.9 mmHg; P>0.59), whereas it increased by 7.0 ± 14.3 mmHg in the regular-salt group (P<0.001). The mean between-group difference was –8.0 mmHg (95%CI: –12.4 to –3.7 mmHg; P<0.001).
- Similarly, the mean diastolic blood pressure did not change in the salt-substitute group (0.2 ± 7.1; P>0.59) but did increase in the regular-salt group (2.1 ± 7.5 mmHg; P<0.001; mean difference:–2.0 mmHg; 95%CI: –4.1 to 0.1 mmHg; P=0.057).
Conclusion
This post-hoc analysis of the DECIDE-Salt trial among Chinese, normotensive, older adults living at different elderly care facilities, replacing regular salt with a potassium-enriched salt substitute for 2 years reduced the incidence of hypertension by 40% compared with continued use of regular salt, without increasing the risk of hypotensive episodes. Additionally, both mean systolic and diastolic BP increased in the regular-salt group but not the salt-substitute group. The authors believe this explains why the salt substitution had different effects on the risks of hypertension and hypotension. “[...], the effect on the incidence of hypertension was actually in stopping BP from further increasing rather than reducing it from the baseline. Hence, salt substitution did not increase the risk of hypotension among individuals with normal BP.”
References
1. Hu J, Zhao L, Thompson B, et al. Effects of salt substitute on home blood pressure differs according to age and degree of blood pressure in hypertensive patients and their families. Clin Exp Hypertens. 2018;40(7):664–672.
2. Zhou X, Liu JX, Shi R, et al. Compound ion salt, a novel low-sodium salt substitute: from animal study to community-based population trial. Am J Hypertens. 2009;22(9):934–942.
3. Bernabe-Ortiz A, Sal Y Rosas VG, Ponce-Lucero V, et al. Effect of salt substitution on community-wide blood pressure and hypertension incidence. Nat Med. 2020;26(3):374–378.
4. Jin A, Liu K, Labarthe DR, et al. Impact of salt substitute and stepwise reduction of salt supply on blood pressure in residents in senior residential facilities: design and rationale of the DECIDE-Salt trial. Am Heart J. 2020;226:198–205. 5. 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. 2023;29(4):973–981.