medwireNews: Switching to salt substitutes reduces blood pressure and cardiovascular (CV) disease events in residents of care homes for the elderly, show the DECIDE-Salt study findings.
But progressively restricting usual salt use to a target 40% reduction had no effect over the course of the 24-month trial, which was conducted in China.
By the end of the study, the 807 residents of 24 facilities randomly assigned to receive a salt substitute in their food (usual or restricted supply) had achieved an average 7.1 mmHg reduction in their systolic blood pressure relative to the 805 residents of 24 facilities who continued with usual salt.
Yangfeng Wu (Peking University School of Public Health, Beijing, China) and co-researchers note that this may have somewhat underestimated the benefits, because subanalyses indicated a stronger effect in women than men, but 76.3% of the study participants were men.
Diastolic blood pressure was a significant average of 1.9 mmHg lower with salt substitute versus salt by month 24, and the rate of major CV events (myocardial infarction, stroke, heart failure, and vascular death) was also significantly lower, at 2.3 versus 3.8 per 100 person–years.
The researchers observe that the effects on blood pressure and CV events were larger than those seen in the Salt Substitute and Stroke Study, which recruited people living in the community.
“Implementation of salt substitution in a collective living setting where residents have limited control over the composition of the food they eat and the seasonings they use would be expected to maximize the effect of the intervention,” they write in Nature Medicine.
The two studies together “strongly and consistently support the more widespread use of salt substitute for [CV disease] prevention,” says the team.
These benefits of salt substitution were associated with a significant increase in average serum potassium and an increased risk for biochemical hyperkalemia, at 7.0% versus 2.4% with usual salt.
Nevertheless, Wu and colleagues found “no evidence of associated adverse clinical outcomes,” which they say “is a new observation and provides reassurance about safety” in these elderly people who typically have higher blood pressure and poorer renal function than younger populations.
They add that the salt substitute used in the study had a “relatively low” potassium content, with 25% potassium chloride, chosen “to maximize benefit and minimize risk.”
In contrast with the benefits of salt substitution, there were no blood pressure differences observed between the 843 residents of 24 facilities who received a progressively restricted supply of salt or salt substitute versus the 769 residents of 24 facilities who continued with their usual intake.
The researchers believe the reasons for this to be “very complex,” potentially including participants noticing the reduced salt and adding nonstudy table salt, facility cooks being unwilling to reduce salt by the necessary amount, and facilities in the salt-as-usual group taking action to reduce their residents’ intake.
“The failure of the salt reduction intervention is a potentially important finding, which raises broader doubts about the feasibility of this strategy in real-world settings,” they conclude.
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Nat Med 2023; doi:10.1038/s41591-023-02286-8