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Trial registered on ANZCTR


Registration number
ACTRN12619000352101
Ethics application status
Approved
Date submitted
22/02/2019
Date registered
6/03/2019
Date last updated
24/10/2019
Date data sharing statement initially provided
6/03/2019
Type of registration
Prospectively registered

Titles & IDs
Public title
Salt ALTernatives Study (SALTS): A smartphone app and dietary alternative salt to lower blood pressure for adults with high blood pressure
Scientific title
Salt ALTernatives Study (SALTS): A randomised controlled trial to determine the effects of a 12-week dietary salt reduction intervention (SaltSwitch app + dietary alternative salt) on systolic blood pressure in adults with high blood pressure
Secondary ID [1] 297497 0
Health Research Council of New Zealand programme grant number: 18/672
Universal Trial Number (UTN)
U1111-1225-4471
Trial acronym
SALTS (Salt ALTernatives Study)
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Hypertension 311685 0
Condition category
Condition code
Cardiovascular 310314 310314 0 0
Hypertension
Diet and Nutrition 310315 310315 0 0
Other diet and nutrition disorders

Intervention/exposure
Study type
Interventional
Description of intervention(s) / exposure
The intervention is designed to lower blood pressure and includies two components: (1) a smartphone application (app) called SaltSwitch, and (2) a dietary alternative salt. The SaltSwitch app helps users to select lower salt packaged foods by enabling them to scan the barcode of a packaged food and receive an immediate, interpretive traffic light nutrition label on-screen plus suggestions for lower salt alternatives. Users can also directly compare the salt content and healthiness of two or more food products. The dietary alternative salt is a blend of potassium salt and sea salt which provides a 75% reduction in sodium compared to regular table salt. The dietary alternative salt comprises 74.5% potassium chloride and 24.5% sodium chloride and ~1% silicon dioxide (anticaking agent). Intervention participants will receive weekly notifications to their smart phone to remind them to use the SaltSwitch app and dietary alternative salt. Participants will be encouraged to use the dietary alternative salt in place of regular table salt in cooking and at the table, but not to use more or less salt than usual. Delivery of the intervention will be entirely remote with the smartphone app downloaded to participants phones during the randomisation phone call, and the dietary alternative salt being sent by courier to the participant shortly thereafter. Google analytics will be used to monitor use of the SaltSwitch app by individual participants who have WiFii, and the amount of dietary alternative salt left over at the end of the 12-week intervention period will be self-reported in household measures (tsp). Use and acceptibility of the SaltSwitch app and dietary alternative salt will also be self-reported in the follow-up questionnaire.
Intervention code [1] 313740 0
Prevention
Intervention code [2] 313836 0
Lifestyle
Intervention code [3] 313837 0
Treatment: Other
Comparator / control treatment
The control group will receive generic information about heart-healthy eating from the Heart Foundation of New Zealand. This will comprise one email at the start of the intervention period with a web-link to heart healthy eating information available on the Heart Foundation of New Zealand website.
Control group
Active

Outcomes
Primary outcome [1] 319202 0
Difference in systolic blood pressure assessed using a home-based blood pressure monitor
Timepoint [1] 319202 0
Week 12 (average of 2x daily measures collected in triplicate for 7 days)
Secondary outcome [1] 367261 0
Difference in systolic blood pressure assessed using a home-based blood pressure monitor
Timepoint [1] 367261 0
Week 6 (average of 2x daily measures collected in triplicate for 7 days)
Secondary outcome [2] 367262 0
Difference in urinary sodium excretion assessed using a spot (casual) urine sample
Timepoint [2] 367262 0
Week 12
Secondary outcome [3] 367263 0
Difference in the sodium content of packaged food purchases assessed using the barcodes of packaged foods purchases linked with a branded food composition database. Participants will scan the barcodes of all packaged foods bought into the home for consumption at baseline (weeks -2 and -1) and weeks 11 and 12 of the 12 week intervention period..
Timepoint [3] 367263 0
Weeks 11 and 12 (average)
Secondary outcome [4] 367264 0
The number of participants achieving BP control assessed using a home-based blood pressure monitor and cut-off of 135/85 mmHg
Timepoint [4] 367264 0
Week 12 (average of 2x daily measures collected in triplicate for 7 days)
Secondary outcome [5] 367265 0
Use of the SaltSwitch app assessed via on-line questionnaire using questions designed specifically for this study.
Timepoint [5] 367265 0
Week 12
Secondary outcome [6] 367266 0
Use of the dietary alternative salt assessed via on-line questionnaire using questions designed specifically for this study.
Timepoint [6] 367266 0
Week 12
Secondary outcome [7] 367756 0
Difference in urinary potassium excretion assessed using a spot (casual) urine sample
Timepoint [7] 367756 0
Week 12
Secondary outcome [8] 367757 0
Acceptability of the SaltSwitch app assessed via on-line questionnaire using questions designed specifically for this study.
Timepoint [8] 367757 0
Week 12
Secondary outcome [9] 367758 0
Acceptability of the dietary alternative salt assessed via on-line questionnaire using questions designed specifically for this study.
Timepoint [9] 367758 0
Week 12

Eligibility
Key inclusion criteria
Aged 18 years or older
Own a smartphone (iPhone or Android)
Have a systolic blood pressure of greater than or equal to 140mmHg and/or diastolic blood pressure of greater than or equal to 85mmHg at screening
Are willing to contribute to grocery shopping during the study period
Are able to read and understand English
Minimum age
18 Years
Maximum age
No limit
Gender
Both males and females
Can healthy volunteers participate?
No
Key exclusion criteria
Currently use a dietary alternative salt
Currently use the FoodSwitch smartphone app
Have a contraindication to changing dietary sodium intake e.g. severe kidney disease or use of a potassium sparing diuretic
Are taking medication that may lead to hyponatraemia or acute build-up of body water such as furosemide, regular NSAID use, or regular prednisone use
Have had a stroke or cardiovascular event (hospitalisation for heart attack, coronary artery revascularisation (CABG or stenting), stroke or heart failure) in the previous 6 months
Have diagnosed heart failure
Do not provide at least six home-based blood pressure measures during week two of baseline (week -2)
Do not return a spot (casual) urine sample at week -1 of baseline
Do not scan at least 30 packaged food products using the trial smartphone app during the two-week baseline period
Are planning on going away for two or more weeks over the next 14 weeks
Are unable to provide informed consent

Study design
Purpose of the study
Prevention
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Allocation will be concealed using centralised randomisation in on-line software (REDCap) .
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
The randomisation sequence will be generated by computer programme. Following baseline data collection, eligible participants will be randomised to either intervention or control group in a 1:1 ratio stratified by ethnicity (Maori and non-Maori) and age (<55yrs and 55yrs+) using stratified block randomisation with variable block sizes of two or four.
Masking / blinding
Blinded (masking used)
Who is / are masked / blinded?



The people analysing the results/data
Intervention assignment
Parallel
Other design features
Phase
Not Applicable
Type of endpoint(s)
Efficacy
Statistical methods / analysis
Study power:
A total of 844 participants (422 per group) will provide 90% power at a 5% level of significance to detect at least 2.5mmHg difference in SBP between groups after the 12-week intervention, assuming a standard deviation (SD) of 10 and allowing for 20% loss to follow-up. The estimated effect size is based on data from the SaltSwitch pilot study, the PATHWAY-2 trial, the DASH study, and a meta-analysis of the effect of lowering sodium on health. The magnitude of change (2.5mmHg) is considered clinically important and would have a significant impact on cardiovascular disease if achieved at a population level.

Statistical analysis:
Statistical analysis will be performed on an intention-to-treat (ITT) basis, using SAS version 9.4 (SAS Institute Inc. Cary NC, USA). All statistical tests will be two-sided at 5% significance level. Trial results will be reported according to CONSORT 2010 guidelines for parallel group randomised trials.
Baseline characteristics of all randomised participants will be summarised using descriptive statistics. Continuous variables will be described as numbers of observed and missing values, mean ± standard deviation. Categorical variables will be described as numbers and percentages. Results will be presented for each of the two treatment arms overall, and by ethnicity (Maori vs non-Maori) and age group (<55yrs and 55yrs+) separately as stratification factors. Since any differences between randomised groups at baseline could only have occurred by chance, no formal significance testing will be conducted.
Treatment evaluation will be performed on the principle of intention-to-treat (ITT), using data collected from all randomised participants. The primary outcome at week 12 will be analysed using linear regression model, adjusting for baseline outcome value and stratification factors. Multiple imputations will be applied to missing data, using the Markov chain Monte Carlo (MCMC) method assuming the data are missing at random. Sensitivity analyses will be conducted using other imputation methods when the proportion of missing data on the primary outcome is greater than 20%. Per protocol analysis will be considered on those participants who provided complete primary outcome data without major protocol deviations. Secondary outcomes will be analysed using generalised linear regression models with a link function appropriate to the distribution of outcome measure. As a secondary approach, the effects of intervention on systolic blood pressure at 6 and 12 weeks will be tested between two groups using random effect mixed model. Both descriptive statistics and model-adjusted estimates of group differences will be reported, with associated 95% CI’s and p-values. The heterogeneity of treatment effects between Maori and non-Maori participants will be tested using an interaction term between treatment group and ethnicity, similar for participants in two different age groups (<55yrs and 55yrs+).
If the intervention is found to be effective, then cost-effectiveness and cost-utility analyses will also be completed. Cost-utility analyses will employ an established Markov model which models the observed change in BP through to a change in Quality Adjusted Life Years (QALYs) and health system costs for the total New Zealand population.
No interim analysis will be undertaken in this trial.
.

Recruitment
Recruitment status
Recruiting
Date of first participant enrolment
Anticipated
Actual
Date of last participant enrolment
Anticipated
Actual
Date of last data collection
Anticipated
Actual
Sample size
Target
Accrual to date
Final
Recruitment outside Australia
Country [1] 21302 0
New Zealand
State/province [1] 21302 0
Auckland

Funding & Sponsors
Funding source category [1] 302060 0
Government body
Name [1] 302060 0
Health Research Council of New Zealand
Address [1] 302060 0
PO Box 5541, Wellesley Street, Auckland 1141
Country [1] 302060 0
New Zealand
Primary sponsor type
University
Name
National Institute for Health Innovation
Address
School of Population Health
The University of Auckland
Private Bag 92019
Auckland Mail Centre
Auckland 1142
Country
New Zealand
Secondary sponsor category [1] 301871 0
None
Name [1] 301871 0
Address [1] 301871 0
Country [1] 301871 0

Ethics approval
Ethics application status
Approved
Ethics committee name [1] 302741 0
Health and Disability Ethics Committees
Ethics committee address [1] 302741 0
Ministry of Health
133 Molesworth Street
PO Box 5013
Wellington
6011
Ethics committee country [1] 302741 0
New Zealand
Date submitted for ethics approval [1] 302741 0
20/12/2018
Approval date [1] 302741 0
17/02/2019
Ethics approval number [1] 302741 0
18/NTB/239

Summary
Brief summary
High blood pressure (BP) alone accounts for 8.3% of health loss in NZ and is a major risk factor for cardiovascular disease, New Zealands leading cause of early death. Adherence to a low salt diet is critical to reduce BP, yet New Zealand adults currently consume ~40% more salt than recommendations, and identifying foods low in salt and changing habits around discretionary salt intake can be challenging. New Zealand does not currently have a national sodium reduction strategy and the food industry has been slow to remove excess salt from packaged foods. Therefore, more effective, scalable dietary salt reduction interventions are urgently needed. The SALTS trial will determine the effects of a dietary salt reduction intervention (SaltSwitch smartphone application (app) + dietary alternative salt) on systolic BP in adults with high BP.
Trial website
Trial related presentations / publications
Public notes

Contacts
Principal investigator
Name 91234 0
Dr Helen Eyles
Address 91234 0
National Institute for Health Innovation
School of Population Health
The University of Auckland
Private Bag 92019
Auckland Mail Centre
Auckland 1142
Country 91234 0
New Zealand
Phone 91234 0
+64 9 9234658
Fax 91234 0
Email 91234 0
h.eyles@auckland.ac.nz
Contact person for public queries
Name 91235 0
Mrs Jacqui Grey
Address 91235 0
National Institute for Health Innovation
School of Population Health
The University of Auckland
Private Bag 92019
Auckland Mail Centre
Auckland 1142
Country 91235 0
New Zealand
Phone 91235 0
+64 9 923 8210
Fax 91235 0
Email 91235 0
jk.grey@auckland.ac.nz
Contact person for scientific queries
Name 91236 0
Dr Helen Eyles
Address 91236 0
National Institute for Health Innovation
School of Population Health
The University of Auckland
Private Bag 92019
Auckland Mail Centre
Auckland 1142
Country 91236 0
New Zealand
Phone 91236 0
+64 9 9234658
Fax 91236 0
Email 91236 0
h.eyles@auckland.ac.nz

Data sharing statement
Will individual participant data (IPD) for this trial be available (including data dictionaries)?
No
No/undecided IPD sharing reason/comment
The data sharing policy and statement for this trial is still be considered.
What supporting documents are/will be available?
No other documents available
Summary results
No Results