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New hypertension cases halved with community-wide salt substitution


 

REPORTING FROM THE ESC CONGRESS 2019

– In rural Peru, a comprehensive community-wide strategy to replace conventional table salt with a formulation that was 25% potassium chloride halved incident hypertension, also dropping blood pressure in participants with baseline hypertension.

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The multifaceted intervention targeted six villages at the far north of Peru, replacing table salt with the lower-sodium substitute, J. Jaime Miranda, MD, PhD, said at a prevention-focused, late-breaking research session at the annual congress of the European Society of Cardiology. The 75/25 mixture had a palatable proportion of potassium, and was easily produced by combining table salt with potassium chloride crystals.

Dr. Miranda, director of the CRONICAS Center of Excellence at the Cayetano Heredia Peruvian University, Lima, and colleagues enrolled virtually all adult residents of the six villages in the study; patients who reported heart disease or chronic kidney disease were excluded.

“We wanted to achieve and shape a pragmatic study – and a pragmatic study that incorporates day-to-day behavior. We eat every day, but we think very little of our salt habits,” said Dr. Miranda in a video interview.

In all, 2,376 of 2,605 potential participants enrolled in the study, which used a stepped-wedge, cluster-randomized, controlled trial design. To track the primary outcome measures of systolic and diastolic BP, measurements were obtained every 5 months for a total of seven rounds of measurement, said Dr. Miranda.

Dr. Miranda said that the investigators borrowed principles from social marketing to ensure community-wide replacement of table salt with the low-sodium substitute. This meant that they branded and packaged the low-sodium salt and gave it to participants at no cost – but with a catch. To receive the low-sodium salt, participants had to turn in their table salt.

The effort was supported by promotional events and a trained “sales force” who brought messaging to families, restaurants, and key voices in the community. The attractively packaged replacement salt was distributed with a similarly branded shaker. “We wanted to guarantee the full replacement of salt in the entire village,” explained Dr. Miranda.

At the end of the study, individuals with hypertension saw a decrease in systolic BP of 1.92 mm Hg (95% confidence interval, –3.29 to –0.54).

New hypertension diagnoses, a secondary outcome measure, fell by 55% in participating villages; the hazard ratio for hypertension incidence was 0.45 (95% CI, 0.31-0.66) in a fully adjusted statistical model that accounted for clustering at the village level, as well as age, sex, education, wealth index, and body mass index, said Dr. Miranda.

Older village residents with hypertension saw greater BP reduction; for those aged at least 60 years, the mean reduction was 2.17 mm Hg (95% CI, –3.67 to –0.68).

The positive findings were met with broad applause during his presentation, a response that made his 15-hour trip from Lima to Paris worthwhile, said Dr. Miranda.

Adherence was assessed by obtaining 24-hour urine samples from a random sample of 100 participants before and after the study. “This was my biggest fear – that as soon as we left the door, people would go and throw it away,” said Dr. Miranda. Among these participants, excreted potassium rose, indicating adherence, but sodium stayed basically the same. Possible explanations included that individuals were adding table salt to their diets, or that other prepared foods or condiments contained high amounts of sodium.

The study shows the feasibility of a community-wide intervention that achieved the dual aims of population-wide reductions in BP and reduction in incident BP, and of achieving clinically meaningful benefits for the high-risk population, said Dr. Miranda. He remarked that the population was young overall, with a mean age of 43 years and a low mean baseline systolic BP of 113, making the modest population-wide reduction more notable.

“We wanted to shift the entire distribution of blood pressure in the village. And with that, we see gains not only in public health, but also effective improvements in blood pressure in those at high risk, particularly those who tend to have high blood pressure,” said Dr. Miranda.

Discussant Bruce Neal, MD, professor of medicine at the University of Sydney and senior director of the George Institute for Global Health in Newtown, Australia, congratulated Dr. Miranda and colleagues on accomplishing “a truly enormous project.” He began by noting that, though the reductions were modest, “the low starting blood pressures were almost certainly responsible for the magnitude of effect seen in this study.” He added that “this is nonetheless a worthwhile blood pressure reduction, particularly if it was sustained throughout life.”

Addressing the lack of decrease in excreted urine sodium, Dr. Neal noted that participants may have supplemented their diet with additional sodium by one means or another, “which might also have attenuated the blood pressure difference – but it could also reflect the challenges of measuring sodium and potassium effectively with 24-hour urine samples, which are difficult to collect.”

The lack of adverse effects was notable, said Dr. Neal. “When considering the use of salt substitute at the population level, the first question that arises is: ‘What about the risks of hyperkalemia?’

“I think those risks are probably greatly overstated,” he said, noting that only individuals with severe chronic kidney disease would likely be affected, and those individuals are already well versed on the importance of avoiding excess dietary potassium.

The study was funded by the National Institutes of Health through the Global Alliance for Chronic Disease program. Dr. Miranda reported that he had no conflicts of interest. Dr. Neal reported that he has financial relationships with Nu-Tec Salt and a Beijing-based salt manufacturer, related to research into salt substitutes.

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