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Trial registered on ANZCTR


Registration number
ACTRN12613001246774
Ethics application status
Approved
Date submitted
6/11/2013
Date registered
13/11/2013
Date last updated
14/11/2013
Type of registration
Prospectively registered

Titles & IDs
Public title
Food purchases of New Zealand adults under different conditions in the Virtual Supermarket (pilot)
Scientific title
The effects of a tax increase, information about a tax and a combination of both on purchases in the Virtual Supermarket by New Zealand adults (pilot)
Secondary ID [1] 283525 0
None
Universal Trial Number (UTN)
U1111-1149-9729
Trial acronym
n/a
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Obesity 290445 0
Condition category
Condition code
Public Health 290834 290834 0 0
Other public health
Diet and Nutrition 290844 290844 0 0
Obesity

Intervention/exposure
Study type
Interventional
Description of intervention(s) / exposure
All participants will be asked to conduct a typical weekly shop in the Virtual Supermarket, which is a three-dimensional software application that has been designed in the image of a real New Zealand supermarket. Upon registration, participants will be blindly randomised to one of the following:

- control
- a 20% tax on sugar sweetened beverages and no information about the tax
- a 20% tax on sugar sweetened beverages and information in the form of a newspaper article about the tax prior to the virtual shop
- a 20% tax on sugar-sweetened beverages and information in the form of in-store labels on taxed products
- a 20% tax on sugar-sweetened beverages and information in the form of both in-store labels on taxed products and a newspaper article about the tax prior to the virtual shop
- no tax on sugar sweetened beverages and information in the form of a newspaper article about the tax prior to the virtual shop
- no tax on sugar-sweetened beverages and information in the form of in-store labels on "taxed" products

Participants randomised to an information condition but no tax will be falsely informed that a tax has been put in place (e.g. taxed label on SSB but no price change)
Intervention code [1] 288228 0
Other interventions
Comparator / control treatment
The control group will be exposed to typical supermarket prices for all goods and will receive no information about a tax
Control group
Active

Outcomes
Primary outcome [1] 290835 0
Differences in sugar-sweetened beverage purchases (in litres) between groups in the virtual shop (participants do not actually purchase the products)
Timepoint [1] 290835 0
End of virtual shopping task
Secondary outcome [1] 305387 0
Self-reported response to sugar-sweetened beverage tax and information

The questionnaire used was designed specifically for this study but incorporates questions from previous studies on the determinants of purchasing decisions.
Timepoint [1] 305387 0
Post-task questionnaire
Secondary outcome [2] 305388 0
Differences in purchases of other product categories in the Virtual Supermarket in the virtual shop

*Beverages (Alcoholic beverages, 100% fruit juices, Milk, Other non-SSBs)
*Baby care
*Bread, bakery, cereal, and cereal products
*Convenience foods, deli and chilled foods
*Dairy and eggs (not milk)
*Edible oils and oil emulsions
*Fruit and vegetables
*Meat, fish and seafood
*Snack foods
Timepoint [2] 305388 0
End of virtual shopping task

Eligibility
Key inclusion criteria
Adult (over 18 years)
Key responsible person in the household for grocery shopping
Speaks and reads English
Has access to a computer and internet
Has an email address
Minimum age
18 Years
Maximum age
No limit
Gender
Both males and females
Can healthy volunteers participate?
Yes
Key exclusion criteria
Participants will be excluded if another member of the household is taking part in the study

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)
Once the participant has been deemed eligible to take part in the trial, the researchers will assign them a unique identifier which they will enter when completing the online virtual shopping task.

The unique identifier contains information about the condition to which the participant has been randomised so that the participant views the Virtual Supermarket task as appropriate to their randomisation condition.

The unique identifier will be generates using simple randomisation by a computer function applied to the case file upon registration by the participant. The condition that the participant is randomised to will not be concealed from the researcher.

Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Simple randomisation using computer function applied to case file upon registration by participant
Masking / blinding
Blinded (masking used)
Who is / are masked / blinded?
The people receiving the treatment/s


Intervention assignment
Parallel
Other design features
Participants will be debriefed at the end of the study period as to what condition they were randomised to, and what the other conditions in the study were. This will be done via email at the end of the data collection (i.e. when all participants have completed the task).
Phase
Not Applicable
Type of endpoint(s)
Efficacy
Statistical methods / analysis
This will be a pilot study aiming to explore how an SSB tax, and information about an SSB tax affect purchases. As this is not a full RCT, no formal power calculation is required. However, previous experience with the Virtual Supermarket experiments showed that a sample of around n = 20 participants per condition is sufficient to obtain significant results. Therefore, the study will aim to recruit at least n = 150 participants.

Demographic data and user feedback will be summarised using descriptive statistics. Continuous variables will be reported as numbers of observed and missing values, mean, standard deviation, median, minimum and maximum. Categorical variables will be reported as frequencies and percentages.

Differences between groups will be determined using ANOVA and associated tests where the variables can be approximated to resemble a normal distribution. Non-parametric tests will be used where the underlying distributions do not resemble a normal distribution.

As this is a pilot study, no adjustments will be made to control for multiple comparisons. The results obtained could be used to inform sample size estimates for future large-scale trials in this area.

Recruitment
Recruitment status
Not yet 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] 5573 0
New Zealand
State/province [1] 5573 0
All

Funding & Sponsors
Funding source category [1] 288223 0
University
Name [1] 288223 0
University of Auckland
Address [1] 288223 0
12 Grafton Road
Grafton
Auckland 1142
Country [1] 288223 0
New Zealand
Primary sponsor type
University
Name
University of Auckland
Address
12 Grafton Road
Grafton
Auckland 1142
Country
New Zealand
Secondary sponsor category [1] 286946 0
None
Name [1] 286946 0
n/a
Address [1] 286946 0
n/a
Country [1] 286946 0

Ethics approval
Ethics application status
Approved
Ethics committee name [1] 290132 0
University of Auckland Human Participants Ethics Committee
Ethics committee address [1] 290132 0
Research Integrity Unit
Level 10, Building 620
49 Symonds Street
Auckland 1142
Ethics committee country [1] 290132 0
New Zealand
Date submitted for ethics approval [1] 290132 0
21/08/2013
Approval date [1] 290132 0
07/10/2013
Ethics approval number [1] 290132 0
010452

Summary
Brief summary
This pilot randomised controlled study aims to examine the effects of a sugar-sweetened beverage (SSB) tax or SSB tax information or a combination of both on purchases and on consumer perceptions using the recently developed New Zealand Virtual Supermarket. The New Zealand Virtual Supermarket is a three-dimensional software application that has been designed in the image of a real New Zealand supermarket.

SSB taxes have been proposed as a method to reduce soft drink consumption (and subsequently reduce calorie intake) and could therefore help to tackle the growing obesity epidemic. Evidence on the effectiveness of soft drink taxes is however very limited and has largely been restricted to modelling studies which are not able to explore how information and knowledge about such a tax (referred to as price salience in the economic literature) would mediate changes in consumption. Moreover, such studies give limited insight in cross-price elasticity and substitution effects (e.g., it has been suggested that increased SSB taxes might result in an increased alcohol intake). Before taxes are implemented on a large scale, it is important to gain more insight into these effects and examine the best design of the tax for public health outcomes. Therefore this study aims to:

1. To examine the differences in SSB purchases between groups of participants exposed to different SSB tax and information scenarios within the Virtual Supermarket.
2. To obtain participant feedback on perceptions of the SSB tax and their intended response to the tax.

Participants (recruited from the general adult NZ population) will be randomized to one of seven conditions (pricing and/or information conditions or control) and will be asked to conduct a weekly household shop in the Virtual Supermarket.

The Virtual Supermarket is a 3-dimensional software application designed in the image of a real supermarket. It models a representative product selection of food items that can normally be found in a NZ supermarket, including a wide range of soft drinks. Participants will be provided with a link to this software and can complete this study from their home computer or any computer with internet access.

This pilot trial will be designed to provide an optimal level of information on the potential effectiveness of different tax and information combinations. We anticipate that this trial will inform the design of a larger trial by identifying the interventions with the largest potential for public health.
Trial website
Trial related presentations / publications
Public notes

Contacts
Principal investigator
Name 44118 0
Dr Wilma Waterlander
Address 44118 0
National Institute for Health Innovation
University of Auckland
Private Bag 92019
Auckland 1142

Country 44118 0
New Zealand
Phone 44118 0
+64 9 373 7599 ext. 84743
Fax 44118 0
+64 9 373 1710
Email 44118 0
w.waterlander@nihi.auckland.ac.nz
Contact person for public queries
Name 44119 0
Dr Wilma Waterlander
Address 44119 0
National Institute for Health Innovation
University of Auckland
Private Bag 92019
Auckland 1142
Country 44119 0
New Zealand
Phone 44119 0
+64 9 373 7599 ext. 84743
Fax 44119 0
+64 9 373 1710
Email 44119 0
w.waterlander@nihi.auckland.ac.nz
Contact person for scientific queries
Name 44120 0
Dr Wilma Waterlander
Address 44120 0
National Institute for Health Innovation
University of Auckland
Private Bag 92019
Auckland 1142
Country 44120 0
New Zealand
Phone 44120 0
+64 9 373 7599 ext. 84743
Fax 44120 0
+64 9 373 1710
Email 44120 0
w.waterlander@nihi.auckland.ac.nz

No information has been provided regarding IPD availability
Summary results
No Results