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Trial registered on ANZCTR


Registration number
ACTRN12620000206921
Ethics application status
Approved
Date submitted
4/02/2020
Date registered
20/02/2020
Date last updated
5/10/2022
Date data sharing statement initially provided
20/02/2020
Date results information initially provided
3/11/2021
Type of registration
Prospectively registered

Titles & IDs
Public title
Effect of a sugar-sweetened beverage price increase on healthiness of purchases and business outcomes in an Australian university
Scientific title
Effect of a 20% sugar-sweetened beverage price increase on healthiness of purchases and business outcomes in an Australian university: a randomised control trial
Secondary ID [1] 299717 0
Nil known
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Sugar-sweetened beverage intake 315063 0
Condition category
Condition code
Diet and Nutrition 313397 313397 0 0
Other diet and nutrition disorders

Intervention/exposure
Study type
Interventional
Description of intervention(s) / exposure
In December 2016, Monash began a transition to healthier food retail vending across their campuses. Monash University adopted the voluntary Victorian Government Healthy Choices guidelines for vending machines in April 2017. These guidelines specify that unhealthy ‘red’ foods and drinks should comprise less than 20% of available items, and healthy ‘green’ food and drink should comprise at least 50% of available items. The focus of the current intervention is on 60 Western-style vending machines which sell both drinks and snacks across the campuses.

The RCT will run on all Victorian Monash campuses for 24 months from March 2020 (beginning of semester 1) to February 2022 (prior to Semester 1 2022). A 2 x 2 factorial design will be used to test the independent and combined effect of two interventions: a 20% price increase on ‘red’ drinks, and the addition of pricing labels at the point-of-selection. The four conditions defined by these two interventions are:
1. 20% price increase on ‘red’ drinks
2. Prominent price labels added to all drinks
3. 20% price increase on ‘red’ drinks + Prominent price labels added to all drinks
4. Control- no prominent price labels or pricing changes

Rectangular price labels will be inserted directly below each item. They will measure approx 2cm high by 7cm wide. They contain the item number (for selection at the payment terminal), the price (text approx 1cm high and 3cm wide) and a round coloured sticker indicating the traffic light classification with a corresponding message (red= "limit"; amber="choose carefully"; or green= "best choice"). Note that all machines at baseline included item labels with the item number and traffic light labels, but no price.

Photographic audits of machines will be conducted by study personnel at at 6 month intervals: month 1 (March 2020), 6 months (planned for September 2020, delayed to December 2020 due to COVID-19 campus closures), 12 months (March 2021), 18 months (September 2021), 24 months (February 2022). This will be used to determine implementation and maintenance of the intervention (i.e. correct display of prices and prominent price labels according to machine allocation), as well as collect covariates for analysis such as machine proximity to Asian-style vending machines.
Intervention code [1] 315982 0
Behaviour
Comparator / control treatment
Group 4- Control Treatment: Baseline prices of sugar-sweetened beverages and all other beverages in vending machines will remain the same
Control group
Active

Outcomes
Primary outcome [1] 321880 0
Volume sales of sugar-sweetened 'red' beverages (L)
This will be assessed using sales data automatically collected through each vending machine payment terminal.
Timepoint [1] 321880 0
Assessed weekly for 2 years of intervention
Secondary outcome [1] 376571 0
Volume sales of 'amber' drinks (L)
This will be assessed using sales data automatically collected through each vending machine payment terminal.
Timepoint [1] 376571 0
Assessed weekly for 2 years of intervention
Secondary outcome [2] 376572 0
Vending machine revenue
This will be assessed using sales data automatically collected through each vending machine payment terminal.
Timepoint [2] 376572 0
Assessed weekly for 2 years of intervention
Secondary outcome [3] 379501 0
Volume sales of healthy 'green' drinks (L)
This will be assessed using sales data automatically collected through each vending machine payment terminal.
Timepoint [3] 379501 0
Assessed weekly for 2 years of intervention
Secondary outcome [4] 379511 0
Number of 'red' drinks sold
This will be assessed using sales data automatically collected through each vending machine payment terminal.
Timepoint [4] 379511 0
Assessed weekly for 2 years of intervention
Secondary outcome [5] 379512 0
Number of 'amber' drinks sold
This will be assessed using sales data automatically collected through each vending machine payment terminal.
Timepoint [5] 379512 0
Assessed weekly for 2 years of intervention
Secondary outcome [6] 379513 0
Number of 'green' drinks sold
This will be assessed using sales data automatically collected through each vending machine payment terminal.
Timepoint [6] 379513 0
Timepoint updated to:
Assessed weekly for 2 years of intervention
Secondary outcome [7] 379514 0
Vending machine drinks revenue ($)
This will be assessed using sales data automatically collected through each vending machine payment terminal.
Timepoint [7] 379514 0
Assessed weekly for 2 years of intervention
Secondary outcome [8] 379515 0
Number of ‘red’, ‘amber’ and ‘green’ food items sold
This will be assessed using sales data automatically collected through each vending machine payment terminal.
Timepoint [8] 379515 0
1) Mean outcome each week for 2 years of intervention 2) Shifts at the starting point of the intervention period, time trends and effect at the end of the intervention period
Secondary outcome [9] 379516 0
Energy (MJ) sold from drinks
This will be assessed using sales data automatically collected through each vending machine payment terminal. Energy content of each beverage will be derived from the manufacturers' website or product packaging.
Timepoint [9] 379516 0
Assessed weekly for 2 years of intervention
Secondary outcome [10] 379517 0
Total sugar (kg) sold from drinks
This will be assessed using sales data automatically collected through each vending machine payment terminal. Sugar content of each beverage will be derived from the manufacturers' website or product packaging.
Timepoint [10] 379517 0
Assessed weekly for 2 years of intervention

Eligibility
Key inclusion criteria
Human participants will be those who utilise eligible vending machines in the course of this study. All beverage vending machines on all campuses of the recruited university are eligible for inclusion.
Minimum age
18 Years
Maximum age
No limit
Sex
Both males and females
Can healthy volunteers participate?
Yes
Key exclusion criteria
None. Note that the vast majority of vending machine users (as university staff and students) are expected to be 18 years or older, However, some campus visitors or students younger than 18 years may also use the machines.

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)
The researcher who determined machine clustering and and organisation of intervention groups (prior to randomization- see sequence generation below), and who will be primarily responsible for data analysis, was not involved in randomisation and will not be aware of intervention allocation until analysis is complete. Randomised was carried out by one member of the research team who will not be involved in analysis.
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
In order to allocate machines to intervention groups, first, machines will be clustered by precinct, so that vending machines in close proximity (e.g. within a library) are allocated to the same treatment group to avoid people moving to a close located machine to elude the price increase (if detected). Next, machine clusters will be grouped into 4 groups to balance the following criteria prioritised in the described order: (1) number of machines per campus; (2) number of machines per cluster; and (3) mean weekly item sales of machines.
These four groups of machines will then be randomised using Microsoft Excel random number generator to the four intervention conditions. Simple randomisation of clusters was not performed, to avoid allocation of the most popular clusters to the same intervention groups.
Masking / blinding
Open (masking not used)
Who is / are masked / blinded?



Intervention assignment
Factorial
Other design features
It is not possible to blind customers to the interventions, but customers will not be explicitly notified of any intervention or that the vending machine is part of a study.
Phase
Not Applicable
Type of endpoint/s
Statistical methods / analysis
We will conduct separate analyses for each of the outcomes of interest. Each vending machine will provide a weekly time series for each of the specified outcomes. Two periods will be identified: pre intervention, July 2019 – Feb 2020; and intervention March 2020- Feb 2022.
We plan to conduct two levels of analysis for each outcome. First, we will compare the mean of the outcome over the 2 year intervention period across the four conditions using a linear model. The model will include the two interventions indicators (presence of prominent price label and presence of price increase on ‘red’ drinks) and their interaction and baseline estimates of the outcome (over the pre-intervention period) to adjust for sale variability across vending machines. Second, we will conduct an interrupted time series analysis (Wagner AK , Soumerai SB et al. 2002, Linden 2015). This will allow for the estimation of shifts at the starting point of the intervention period, time trends and effect at the end of the intervention period for the four conditions. In both approaches, we will run models additionally including indicator variables for: co-location of Asian vending machines; campus; residential area; and touchpad interface to adjust for potential confounding; and cluster (as random variable).
In the reporting of results, we will note, where relevant, the proportional change in intervention outcome compared to the baseline period. We will also describe the relative healthiness of overall sales by reporting volume sales of red, amber, and green drinks as a proportion of total volume at baseline, and comparing that to each intervention conditions. Only proportional changes will be reported for revenue outcomes as per our commercial-in-confidence agreement.

Recruitment
Recruitment status
Completed
Date of first participant enrolment
Anticipated
2/03/2020
Actual
2/03/2020
Date of last participant enrolment
Anticipated
2/03/2020
Actual
2/03/2020
Date of last data collection
Anticipated
25/02/2022
Actual
25/02/2022
Sample size
Target
60
Accrual to date
Final
59
Recruitment in Australia
Recruitment state(s)
VIC

Funding & Sponsors
Funding source category [1] 304638 0
University
Name [1] 304638 0
Deakin University
Country [1] 304638 0
Australia
Primary sponsor type
Individual
Name
Dr Miranda Blake
Address
Deakin University
221 Burwood Highway, Burwood, VIC 3125
Country
Australia
Secondary sponsor category [1] 304936 0
None
Name [1] 304936 0
Address [1] 304936 0
Country [1] 304936 0
Other collaborator category [1] 281127 0
Individual
Name [1] 281127 0
Jane Dancey
Address [1] 281127 0
Monash University Wellington Rd, Clayton VIC 3800
Country [1] 281127 0
Australia
Other collaborator category [2] 281155 0
Individual
Name [2] 281155 0
Liliana Orellana
Address [2] 281155 0
Deakin University
221 Burwood Highway
Victoria 3125
Country [2] 281155 0
Australia
Other collaborator category [3] 281156 0
Individual
Name [3] 281156 0
Adrian Cameron
Address [3] 281156 0
Deakin University
221 Burwood Highway
Victoria Australia 3125
Country [3] 281156 0
Australia
Other collaborator category [4] 281157 0
Individual
Name [4] 281157 0
Anna Peeters
Address [4] 281157 0
Deakin University
221 Burwood Highway
Victoria Australia 3125
Country [4] 281157 0
Australia
Other collaborator category [5] 281158 0
Individual
Name [5] 281158 0
Julie Brimblecombe
Address [5] 281158 0
Monash University Wellington Rd, Clayton VIC 3800
Country [5] 281158 0
Australia

Ethics approval
Ethics application status
Approved
Ethics committee name [1] 304660 0
Deakin University Human Research Ethics Committee
Ethics committee address [1] 304660 0
Deakin Research Integrity
Deakin University
221 Burwood Hwy
Burwood, VIC 3125
Australia
Ethics committee country [1] 304660 0
Australia
Date submitted for ethics approval [1] 304660 0
02/12/2019
Approval date [1] 304660 0
07/01/2020
Ethics approval number [1] 304660 0
HEAG-H 175_2019
Ethics committee name [2] 305058 0
Monash University Human Research Ethics Committee
Ethics committee address [2] 305058 0
Monash University
Wellington Rd, Clayton VIC 3800
Ethics committee country [2] 305058 0
Australia
Date submitted for ethics approval [2] 305058 0
08/01/2020
Approval date [2] 305058 0
28/01/2020
Ethics approval number [2] 305058 0
Project Number: 23084

Summary
Brief summary
This 2 year randomised controlled trial (RCT) aims to test the effect of two interventions (i) a 20% ‘red’ drink price increase, and (ii) prominent price labelling, on healthiness of vending purchases (‘red’, ‘amber’, and ‘green’ volume sales) and vending revenue in a university. We hypothesise that the price increase and combined price and prominent price labelling, will be associated with a decrease in 'red' drinks purchases. This study will help inform vending machine pricing interventions and potential policies for universities and other institutions who wish to promote customers’ health, while considering the business outcomes for retailers.
Trial website
Trial related presentations / publications
Public notes
This study involves indirect assignment of human participants (vending machine customers) to a behavioural intervention, and the outcomes are surrogates for human behavioural outcomes.

Contacts
Principal investigator
Name 97758 0
Dr Miranda Blake
Address 97758 0
Deakin University
221 Burwood Highway, Burwood, VIC 3125
Country 97758 0
Australia
Phone 97758 0
+61 3 9246 8487
Fax 97758 0
Email 97758 0
[email protected]
Contact person for public queries
Name 97759 0
Dr Miranda Blake
Address 97759 0
Deakin University
221 Burwood Highway, Burwood, VIC 3125
Country 97759 0
Australia
Phone 97759 0
+61 3 9246 8487
Fax 97759 0
Email 97759 0
[email protected]
Contact person for scientific queries
Name 97760 0
Dr Miranda Blake
Address 97760 0
Deakin University
221 Burwood Highway, Burwood, VIC 3125
Country 97760 0
Australia
Phone 97760 0
+61 3 9246 8487
Fax 97760 0
Email 97760 0
[email protected]

Data sharing statement
Will individual participant data (IPD) for this trial be available (including data dictionaries)?
No
No/undecided IPD sharing reason/comment
This data has been given to the researchers by the vending machine supplier under a commercial-in-confidence agreement.


What supporting documents are/will be available?

No Supporting Document Provided



Results publications and other study-related documents

Documents added manually
No documents have been uploaded by study researchers.

Documents added automatically
No additional documents have been identified.