Effectiveness of a Sodium-Reduction Smartphone App and Reduced-Sodium Salt to Lower Sodium Intake in Adults With Hypertension: Findings From the Salt Alternatives Randomized Controlled Trial

JMIR mHealth and uHealth · 10 authors, 5 centres

AI SUMMARY

FIDELITY 100%

POPULATIONAdults aged ≥18 years with high blood pressure (≥140/85 mm Hg) who owned a smartphone and planned to undertake household grocery shopping in New Zealand.

INTERVENTIONA sodium-reduction package comprising the SaltSwitch smartphone app (for scanning packaged foods to choose lower-salt options) and a reduced-sodium salt (RSS) substitute (75% lower sodium than regular salt).

COMPARISONControl group receiving generic heart-healthy eating information from The Heart Foundation of New Zealand.

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AGENT 01 · STRUCTURED SUMMARY

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TL;DR

This randomized controlled trial tested a 12-week intervention package (SaltSwitch smartphone app + reduced-sodium salt) in adults with hypertension to lower sodium intake. The trial found no significant reduction in estimated 24-hour urinary sodium excretion or blood pressure, likely due to low intervention engagement and the trial being underpowered from COVID-19 and recruitment challenges.

Full summary

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BACKGROUND

High blood pressure is a leading cause of premature death, and reducing dietary sodium can lower blood pressure. This trial evaluated a combined intervention (SaltSwitch app + reduced-sodium salt) to reduce sodium intake in adults with hypertension in New Zealand. Methods: A 2-arm parallel RCT randomized 168 adults (84 per group) to the intervention package or generic heart-healthy eating information. The primary outcome was estimated 24-hour urinary sodium excretion at 12 weeks, measured via spot urine. Secondary outcomes included potassium excretion, blood pressure, and sodium content of food purchases. Analyses were intention-to-treat, adjusting for baseline values, age, and ethnicity. Key Results: The trial found no significant difference between groups for the primary outcome (adjusted mean difference 547 mg/day, 95% CI −331 to 1424) or any secondary outcomes, including blood pressure (systolic difference −0.66 mm Hg, 95% CI −3.48 to 2.16). Intervention engagement was low: 75% of intervention participants used the app, but on only about 6 shopping occasions, and RSS consumption was approximately 1/2 teaspoon per household per week. The trial was underpowered due to recruitment challenges and COVID-19 disruptions, with only 168 participants randomized (target 326). Limitations: The study was underpowered, had low engagement with the intervention, used spot urine instead of 24-hour collection, and had low recruitment of Māori and Pacific participants. Implications: The null findings suggest the intervention package did not reduce sodium intake in this population, possibly due to low intervention dose. Future research should explore more effective behavior change techniques, the use of RSSs in packaged foods, and strategies to improve engagement and equity in similar populations.

PICO

PPOPULATION

Adults aged ≥18 years with high blood pressure (≥140/85 mm Hg) who owned a smartphone and planned to undertake household grocery shopping in New Zealand.

IINTERVENTION

A sodium-reduction package comprising the SaltSwitch smartphone app (for scanning packaged foods to choose lower-salt options) and a reduced-sodium salt (RSS) substitute (75% lower sodium than regular salt).

OOUTCOME

Primary outcome: estimated 24-hour urinary sodium excretion at 12 weeks (via spot urine). Secondary outcomes: urinary potassium excretion, blood pressure (systolic and diastolic), sodium content of food purchases, and intervention use/acceptability.

STUDY TYPE

RCT

SPECIALTY

cardiology

SUMMARISED BY

AI pipeline

FIDELITY CHECK

100% · A

ORIGINAL PAPER

PMC10037177

Effectiveness of a Sodium-Reduction Smartphone App and Reduced-Sodium Salt to Lower Sodium Intake in Adults With Hypertension: Findings From the Salt Alternatives Randomized Controlled Trial

JMIR mHealth and uHealth

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ABSTRACT

Background Even modest reductions in blood pressure (BP) can have an important impact on population-level morbidity and mortality from cardiovascular disease. There are 2 promising approaches: the SaltSwitch smartphone app, which enables users to scan the bar code of a packaged food using their smartphone camera and receive an immediate, interpretive traffic light nutrition label on-screen alongside a list of healthier, lower-salt options in the same food category; and reduced-sodium salts (RSSs), which are an alternative to regular table salt that are lower in sodium and higher in potassium but have a similar mouthfeel, taste, and flavor. Objective Our aim was to determine whether a 12-week intervention with a sodium-reduction package comprising the SaltSwitch smartphone app and an RSS could reduce urinary sodium excretion in adults with high BP. Methods A 2-arm parallel randomized controlled trial was conducted in New Zealand (target n=326). Following a 2-week baseline period, adults who owned a smartphone and had high BP (≥140/85 mm Hg) were randomized in a 1:1 ratio to the intervention (SaltSwitch smartphone app + RSS) or control (generic heart-healthy eating information from The Heart Foundation of New Zealand). The primary outcome was 24-hour urinary sodium excretion at 12 weeks estimated via spot urine. Secondary outcomes were urinary potassium excretion, BP, sodium content of food purchases, and intervention use and acceptability. Intervention effects were assessed blinded using intention-to-treat analyses with generalized linear regression adjusting for baseline outcome measures, age, and ethnicity. Results A total of 168 adults were randomized (n=84, 50% per group) between June 2019 and February 2020. Challenges associated with the COVID-19 pandemic and smartphone technology detrimentally affected recruitment. The adjusted mean difference between groups was 547 (95% CI −331 to 1424) mg for estimated 24-hour urinary sodium excretion, 132 (95% CI −1083 to 1347) mg for urinary potassium excretion, −0.66 (95% CI −3.48 to 2.16) mm Hg for systolic BP, and 73 (95% CI −21 to 168) mg per 100 g for the sodium content of food purchases. Most intervention participants reported using the SaltSwitch app (48/64, 75%) and RSS (60/64, 94%). SaltSwitch was used on 6 shopping occasions, and approximately 1/2 tsp per week of RSS was consumed per household during the intervention. Conclusions In this randomized controlled trial of a salt-reduction package, we found no evidence that dietary sodium intake was reduced in adults with high BP. These negative findings may be owing to lower-than-anticipated engagement with the trial intervention package. However, implementation and COVID-19–related challenges meant that the trial was underpowered, and it is possible that a real effect may have been missed. Trial Registration Australian New Zealand Clinical Trials Registry ACTRN12619000352101; https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=377044 and Universal Trial U1111-1225-4471

CITATION EXPORT

Helen Eyles, Jacqueline Grey, Yannan Jiang et al.. Effectiveness of a Sodium-Reduction Smartphone App and Reduced-Sodium Salt to Lower Sodium Intake in Adults With Hypertension: Findings From the Salt Alternatives Randomized Controlled Trial. JMIR mHealth and uHealth. (2023). https://doi.org/10.2196/43675

AUTHORS

10 · 5 CENTRES

Helen Eyles, Jacqueline Grey, Yannan Jiang, Elaine Umali, Rachael McLean, Lisa Te Morenga, Bruce Neal, Anthony Rodgers, Robert N Doughty, Cliona Ni Mhurchu

1 National Institute for Health Innovation The University of Auckland Auckland New Zealand
2 Department of Preventive and Social Medicine University of Otago Dunedin New Zealand
3 Research Centre for Hauora and Health Massey University Wellington Wellington New Zealand
4 The George Institute for Global Health University of New South Wales Sydney Australia
5 Department of Medicine The University of Auckland Auckland New Zealand

EDITOR / REVIEWER

Gunther Eysenbach, Lorraine Buis, Michael Dorsch, Sarah Payne