Clinical Trial Details
— Status: Completed
Administrative data
| NCT number |
NCT05429528 |
| Other study ID # |
7202186 |
| Secondary ID |
|
| Status |
Completed |
| Phase |
N/A
|
| First received |
|
| Last updated |
|
| Start date |
December 28, 2022 |
| Est. completion date |
July 31, 2023 |
Study information
| Verified date |
October 2023 |
| Source |
Duke-NUS Graduate Medical School |
| Contact |
n/a |
| Is FDA regulated |
No |
| Health authority |
|
| Study type |
Interventional
|
Clinical Trial Summary
Using a 3-arm randomized controlled trial, the investigators aim to rigorously evaluate the
effects of two different taxation policies on diet quality. The first is an implicit sales
tax that will be levied only on beverages in a manner that mirrors the current Kingdom of
Saudi Arabia (KSA) beverage taxes and the second is an explicit Nutri-Score (NS) based tiered
tax that is levied on all food and beverage products. The investigators will use an
experimental online grocery store, called NUSMart, which is similar in design to commercial
web-based grocery stores to test these two taxation policies. Participants will be randomly
assigned to one of the following arms and asked to complete a one-time hypothetical shop.
Arm 1 (Control): Participants will experience a default version of NUSMart which replicates
the traditional shopping experience of online grocery stores with no FOP labels.
Arm 2 (Implicit Tax): Same as Arm 1 NUSMart except that an implicit tax will be levied only
on beverages: a 50% sales tax on carbonated drinks and sugar-sweetened beverages (SSBs) and
100% tax on energy drinks (milk, milk-based products, and natural fruit juice are excluded).
Arm 3 (Explicit Tiered Tax): Same as Arm 1 NUSMart except that an explicit tiered tax based
on (underlying) NS is levied on (sale price of) all food and beverages. NS assesses overall
nutritional quality of products on the basis of 7 nutrients (calories, saturated fats, sugar,
salt, fiber, protein and percentage of fruits, vegetables and nuts) from A to E (best to
worst). In this arm, the investigators implement a 20% sales tax on the retail price for NS D
beverages and 10% for NS D foods along with a 50% sales tax on NS E beverages and 20% on NS E
foods.
The investigators hypothesize the following:
Hypothesis 1: Diet quality of food purchases, measured by the weighted average Nutri-Score
point, will be highest in the explicit tiered tax arm, followed by the implicit tax arm,
followed by the control.
Hypothesis 2: Average calories, sugar, sodium, and saturated fat per serving will be lowest
in the explicit tiered tax arm, followed by the implicit tax arm, followed by the control.
Description:
Experimental design & procedures
The aim of this study is to use a 3-arm randomized controlled trial with an online grocery
store known as NUSMart, to rigorously evaluate the effect of two different taxation policies
i.e., implicit tax on select beverages and an explicit tiered tax on all products, on diet
quality.
1. Tax Strategies
The investigators tested 2 different types of taxation strategies in this study. They
are as follows:
1. Implicit Tax: This will be levied only on certain beverage categories: a 50% sales
tax on carbonated drinks and sugar-sweetened beverages (SSBs) and 100% tax on
energy drinks (milk, milk-based products, and natural fruit juice are excluded).
2. Explicit Tiered Tax: This is an explicit tiered tax based on (underlying)
Nutri-Score (NS) grades which will be levied on all food and beverages. In this
arm, the investigators implement a 20% sales tax on the retail price for NS D
beverages and 10% for NS D foods along with a 50% sales tax on NS E beverages and
20% on NS E foods. The NS labels will not be displayed.
2. Overview of RCT Design
To test these labels, the investigators used three different versions of NUSMart. Each
participant was randomly assigned to one of the following arms and asked to complete a
one-time hypothetical shop.
Arm 1: Control arm. Participants experience an unmodified version of NUSMart, which
replicates the traditional shopping experience of online grocery stores.
Arm 2: Similar to Arm 1 except that an implicit tax is levied on qualifying beverages.
Arm 3: Similar to Arm 1 except that an explicit tiered tax is levied on qualifying food
and beverage products.
To minimize hypothetical shopping biases, the investigators set a minimum spending value
per person per week and adjusted the total minimum spending value depending on household
size. Additionally, participants will have to shop from 4 different NUSMart categories
and purchase at least one beverage product to be able to successfully checkout their
cart. Finally, participants will be told that there is up to a 50% probability that they
will be asked to actually purchase the items in their final checked-out cart when in
reality they will never be asked to make any purchase.
3. Subject related procedures
As the investigators have done in prior studies, participants will be recruited if they are
KSA residents aged 18 years or older, can speak Arabic and are primary weekly shoppers for
their households. Recruitment will be done through Facebook advertisements boosted using an
automation tool called Revealbot to help optimise workflow.
On recruitment, they will be asked to fill in a baseline questionnaire to collect demographic
and health characteristics, which should take approximately 10-15 minutes to complete. The
baseline questionnaire includes a question as to whether any household members have a medical
condition, such as diabetes or hypertension, which requires limiting the types of foods they
eat. Investigators ask this question to allow for testing whether the interventions
differentially influence these households, with the expectation that households with less
healthy patients may obtain greater benefits from purchasing baskets with higher mean
Nutri-Scores. Since the objective of this randomized control trail (RCT) is to quantify the
effectiveness of the interventions on diet quality, a precursor to NCDs, the collection of
household health indicators is reasonable.
Upon completion of the baseline survey, participants will be randomly assigned to one of the
3 shopping conditions (Arm 1 [Control], Arm 2, or Arm 3) and redirected to NUSMart to log in
and begin shopping immediately.
On NUSMart, they will be asked to purchase their weekly groceries with a minimum spend of SAR
75 (equivalent to 20 USD) per person per week (the total minimum spending value will depend
on the household size). Each participant will therefore shop only once during the study in
one of the arms (1, 2 or 3) which will be randomly assigned to them.
Participants will be given explicit instructions to purchase groceries for the purposes of
breakfast, lunch, dinner, snacks, and beverage consumption for one week keeping in mind that
they will not be consuming any meals outside. The stores will be set up such that
participants will not be allowed to check out with their cart unless they have selected items
from 4 different NUSMart categories and purchase at least one beverage. This is to ensure
that participants shop as though they are shopping for their own consumption i.e., to
minimize hypothetical biases. As mentioned earlier, participants will be reminded that there
is up to a 50% probability that they will be asked to actually purchase the products in the
final cart they check out from the store.
A post-study survey will be conducted after the shop to collect participant opinions on the
labels and understand their impact better.
