PARIS -- A community-wide salt substitution intervention improved blood pressure and hypertension control levels, a pragmatic trial from Peru showed.
Providing all families, shops, bakeries, and restaurants free salt with potassium chloride replacing 25% of the sodium chloride in exchange for their supply of full-sodium salt for 3 years reduced blood pressure by an average 1.23/0.72 mm Hg (P=0.004 and P=0.022, respectively).
The effect was greater for the 18% of individuals with hypertension and those 60 and older, with significant reductions of 1.92 and 2.17 mm Hg on average, J. Jaime Miranda, MD, PhD, of the Universidad Peruana Cayetano Heredia in Lima, reported here at the European Society of Cardiology meeting.
Cumulative probability of hypertension over the 3 years of the study was reduced 55% compared with controls (P<0.001, using the then-current thresholds of 140 mm Hg systolic and 90 mm Hg diastolic), he announced to a round of audience applause at the late-breaking clinical trial session at the conference, which this year has a global health theme.
"The 15 hours on the plane was worthwhile, thanks guys," he responded, before receiving further accolades at the end of the presentation from session moderator Keith Fox, MBChB, of the University of Edinburgh, Scotland. Fox called not only the result but also its innovative design "very impressive."
There were also no adverse events of note.
The trial used a stepped-wedge cluster design for six semi-rural agricultural and fishing villages in the Tumbes region of Peru, near the border with Ecuador. All adults 18 and older were approached, and 91.2% of the 2,605 enrolled. Individuals with chronic kidney disease, heart disease, or digoxin use were excluded due to concerns about potassium intake. Blood pressure measurement occurred every 5 months for seven rounds, with the pre-implementation measurements acting as controls.
The modest impact on blood likely reflected the low baseline blood pressure of the population there (mean 113.1/72 mm Hg) and would have an important population-level impact, especially if lifelong, noted session study discussant Bruce Neal, MBChB, PhD, of the George Institute for Global Health in Sydney.
Although the average reductions seen with the intervention may seem trivial, lowering systolic pressure by 2 mm Hg can be expected to reduce stroke mortality by 10% and ischemic heart disease and other vascular deaths by 7%, Miranda noted.
"We know that waiting to put people on medication, wait until we get them into the clinic, has shown heavy failure" in achieving public health hypertension goals, whereas this population-level strategy is feasible and effective, he concluded.
But Neal questioned the results in light of the 24-hour urine analysis.
Sodium excretion remained unchanged in the random subsample of 600 participants from baseline to study's end (3.94 vs 3.95 g). Potassium increased from 1.97 to 2.60 g (P<0.001).
"Only about three-quarters of potassium is excreted in urine, so the difference in consumption is actually greater than indicated in that result," Neal noted. "One would have expected to get a substantial decline in sodium. This means either that the individuals were supplementing their diet with additional salt, which might have attenuated the population difference. But it could also reflect the challenges of actually measuring sodium and potassium effectively in 24-hour urine samples, which are difficult to do."
"The effect on incident hypertension was very large and somewhat incongruent with the blood pressure effect. It's not clear to me exactly how to marry up these data," Neal said.
Miranda, though, saw it as proof that people were using the salt substitute. "My biggest fear was as soon as we left the door people would throw it away."
He suggested the effect could be potassium supplementation, not just sodium reduction.
While sodium intake poses a challenge outside of Peru as well, processed foods rather than those prepared at home or in restaurants pose the biggest contributor to intake in the U.S., noted Andrew Kates, MD, of Washington University School of Medicine in St. Louis and a member of the American College of Cardiology's section on prevention.
Reaping the benefits would take buy-in from regulators and the food industry, he suggested, so that it becomes "part of the process where people don't even know about it -- It's the pill in the hamburger approach."
The study was funded by the NHLBI and Global Alliance for Chronic Diseases.
Miranda disclosed no financial relationships with industry.
European Society of Cardiology
Source Reference: Miranda JJ, et al "Salt substitution and community-wide reductions in blood pressure and hypertension incidence" ESC 2019; Abstract 3181.
Read the original article on Medpage Today: Salt Substitute Shakes Up Hypertension in Community Trial