The effect of capping cigarette pack size on consumption
| ISRCTN | ISRCTN16013277 |
|---|---|
| DOI | https://doi.org/10.1186/ISRCTN16013277 |
- Submission date
- 03/03/2020
- Registration date
- 06/03/2020
- Last edited
- 08/04/2024
- Recruitment status
- No longer recruiting
- Overall study status
- Completed
- Condition category
- Other
Plain English summary of protocol
Background and study aims
There is a lack of evidence regarding the impact of cigarette pack sizes (the number of cigarettes per pack) on the number of cigarettes people smoke. The aim of this study is to estimate the impact of asking smokers to buy cigarettes in smaller pack sizes on how many cigarettes they smoke. The results of this study will contribute to policy questions on whether cigarette pack sizes should be capped at 20 cigarettes per pack.
Who can participate?
Adult smokers living in Canada who currently smoke factory-made cigarettes from pack sizes of 25.
What does the study involve?
Participants will be asked to purchase their usual brand variant of cigarettes in pack sizes of 20 for 2 weeks and in pack sizes of 25 for 2 weeks. Participants will be asked to attach stickers to all of the cigarette packs they finish in both of these 2-week periods and fill in information about how many cigarettes they smoked. Participants will then send photos of the packs to the researchers and fill in online surveys about their smoking.
What are the possible benefits and risks of participating?
Participants will be helping to further the understanding of the effect of cigarette pack sizes on smoking and will be able to look up the findings of the study at the research team website (http://www.behaviourchangebydesign.iph.cam.ac.uk). Participants will receive a cheque as remuneration for their time spent completing the study.
Where is the study run from?
1. University of Cambridge (UK)
2. University of Waterloo (UK)
When is the study starting and how long is it expected to run for?
June 2019 to June 2021
Who is funding the study?
The study is funded by the Collaborative Award in Science from Wellcome Trust (Behaviour Change by Design: 206853/Z/17/Z) awarded to Theresa Marteau, Paul Fletcher, Gareth Hollands and Marcus Munafò. The funder is not involved in the study design or data analysis.
Who is the main contact?
Prof. Theresa Marteau
tm388@medschl.cam.ac.uk
Contact information
Scientific
Institute of Public Health
University of Cambridge
Robinson Way
Cambridge
CB2 0SR
United Kingdom
 ORCID ID |
0000-0003-3025-1129 |
|---|---|
| Phone | +44 (0)1223 762567 |
| tm388@medschl.cam.ac.uk |
Study information
| Study design | Interventional randomized crossover trial |
|---|---|
| Primary study design | Interventional |
| Secondary study design | Randomised cross over trial |
| Study setting(s) | Home |
| Study type | Prevention |
| Participant information sheet | Not available in web format, please use contact details to request a participant information sheet. |
| Scientific title | Cigarette pack size and consumption: a randomized crossover trial |
| Study objectives | Reducing cigarette pack sizes from 25 to 20 reduces average consumption by 1.5 cigarettes per day. |
| Ethics approval(s) | 1. Approved 08/11/2019, University of Cambridge Psychology Research Ethics Committee (Cheryl Torbett, Administrator of the Cambridge Psychology Research Ethics Committee, School of the Biological Sciences, 17 Mill Lane, Cambridge, UK; +44 (0)1223 766894; Cheryl.Torbett@admin.cam.ac.uk), ref: PRE.2019.068 2. Approved 30/10/2019, Human Research Ethics Committee at the University of Waterloo (Joanna Eidse, 200 University Avenue West, Waterloo, ON, N2L 3G1, Canada; +1 (0)519-888-4567 ext. 37163; jeidse@uwaterloo.ca), ref: ORE 41353 |
| Health condition(s) or problem(s) studied | Tobacco control |
| Intervention | Participants will be recruited through a research agency, LegerWeb from across Canada. Participants will not be informed of the true aim of the study at the beginning. Participants will be asked to buy their usual brand variant of cigarettes in single pack sizes of 20 cigarettes per pack for a period of 2 weeks (the intervention) and asked for a second period of 2 weeks to buy their usual brand variant of cigarettes in single pack sizes of 25 (the control). Randomisation will occur once participants have been deemed eligible. Participants will be randomised into one of two treatment orders. Treatment order one participants will be asked to consume pack sizes of 20 cigarettes for 2 weeks, followed by a 1-week washout period, followed by 2 weeks of consuming pack sizes of 25 cigarettes (B-A, where B is the intervention and A is the control). Treatment order two participants will be asked to consume pack sizes of 25 cigarettes for 2 weeks, followed by a 1-week washout period, followed by 2 weeks of consuming pack sizes of 20 cigarettes (A-B). Allocation of participants to the order in which they will complete the conditions will be determined using a computer-generated random number sequence prepared by the senior project statistician, using Stata version 15 (StataCorp LLC, TX, USA). Block randomisation will be used to generate an equal number of participants allocated to each treatment order and to reduce the potential of selection bias compared to simple randomisation. The random number sequence, with IDs for the sequence of potential participants, will be concealed from the research team and participant until the participant has consented to taking part in the study and shown that they are able to purchase their usual brand variant of cigarettes in packs of 20 and packs of 25. When a participant is deemed eligible for randomisation, the research team will access the next random allocation in the sequence, and this participant will be assigned the corresponding ID. Participants will be informed of their allocation. They will subsequently be followed up with an email to check receipt of their instructions and understanding of the study procedures. Once outcome data have been collected this will be collated and transferred to the University of Bristol. Before transfer, the field referring to allocation will be coded as X or Y according to the allocation. The data analyst who will conduct the analyses will not be informed of which of X or Y refers to participants who start with pack sizes of 20 or participants who start with pack sizes of 25. |
| Intervention type | Behavioural |
| Primary outcome measure | The average number of cigarettes smoked per day by participants during the two 2-week periods, calculated by adding up all of the cigarettes smoked within each study period and dividing by 14 to obtain a measure of daily consumption. The number of cigarettes smoked will be assessed from photographs participants take of their empty cigarette packs labelled with stickers with the following information: 1. Date pack finished 2. Number of cigarettes smoked by participant from this pack (excluding those given away or not consumed by the participant for any other reason) 3. Number of cigarettes smoked by participant not from that pack while that pack has been open (e.g. given to them by a friend) |
| Secondary outcome measures | Motivation to stop smoking measured using the Motivation to Stop Scale (MTSS) with responses to the question: Which of the following describes you? Responses range from (1) I don’t want to stop smoking to (7) I REALLY want to stop smoking and intend to in the next month. Assessed at two timepoints: at the end of the intervention period and at the end of the control period. |
| Overall study start date | 06/06/2019 |
| Completion date | 24/06/2021 |
Eligibility
| Participant type(s) | Healthy volunteer |
|---|---|
| Age group | Adult |
| Lower age limit | 19 Years |
| Sex | Both |
| Target number of participants | 210 |
| Total final enrolment | 254 |
| Key inclusion criteria | 1. Aged 19 years and over 2. Smoke factory-made cigarettes 3. Have smoked at least 100 cigarettes in their lifetime 4. Currently smoke 10 or more cigarettes a day on every day of the week 5. Normally purchase cigarettes in packs of 25 6. Use a brand or brand variant in which cigarettes are available in pack sizes of 20 as well as 25 in a shop convenient to them 7. Live anywhere in Canada outside of British Columbia, Northwest Territories, Nunavut and Yukon. (The province of British Columbia only sells packs of 20 cigarettes. All other provinces sell packs of both 20s and 25s) 8. Able to read and write sufficient English to complete all study procedures 9. Willing to record on each cigarette pack dates when the pack was opened and when finished 10. Willing to send photos for 4 weeks of their completed cigarette packs 11. Willing to purchase and smoke their usual brand variant in packs of 20 for 2 weeks |
| Key exclusion criteria | 1. Pregnant women and women trying to become pregnant 2. Intend to quit smoking in the next 3 months 3. Used e-cigarettes weekly over the past month, and intend to continue 4. Smoked roll-your-own (RYO) cigarettes once a week or more over the past month and intend to continue 5. Normally transfer cigarettes into a case 6. Do not usually buy their own cigarettes 7. Live in the same household as someone who has enrolled in the study |
| Date of first enrolment | 06/07/2020 |
| Date of final enrolment | 27/04/2021 |
Locations
Countries of recruitment
- Canada
- England
- United Kingdom
Study participating centres
Robinson Way
Cambridge
CB2 0SR
United Kingdom
Waterloo
N2L3G1
Canada
Sponsor information
University/education
Cambridge Research Office
16 Mill Lane
Cambridge
CB2 1SB
England
United Kingdom
| Phone | +44 (0)1223 769291 |
|---|---|
| Research_Governance@medschl.cam.ac.uk | |
| Website | http://www.cam.ac.uk/ |
"ROR" |
https://ror.org/013meh722 |
Funders
Funder type
Research organisation
Private sector organisation / International organizations
- Location
- United Kingdom
Results and Publications
| Intention to publish date | 30/04/2022 |
|---|---|
| Individual participant data (IPD) Intention to share | Yes |
| IPD sharing plan summary | Stored in publicly available repository |
| Publication and dissemination plan | The findings from this study will be published in at least one scientific journal in 2021 and made available open access. They will also be presented at one or more scientific meetings. |
| IPD sharing plan | The data will be made available for sharing via the University of Cambridge Research Data Repository or Open Science Framework online data repository once the findings have been published. Anonymised, participant-level data will be uploaded to the University of Cambridge Data Repository (https://www.data.cam.ac.uk/repository). This website allows anyone to search for data output from studies at the University of Cambridge. Participants consent to anonymised data being made available to other researchers. |
Study outputs
| Output type | Details | Date created | Date added | Peer reviewed? | Patient-facing? |
|---|---|---|---|---|---|
| Protocol file | version v1.8 | 03/03/2020 | 06/03/2020 | No | No |
| Protocol file | version v1.9 | 02/07/2020 | 02/07/2020 | No | No |
| Statistical Analysis Plan | version 12 | 30/06/2021 | 05/07/2021 | No | No |
| Statistical Analysis Plan | version v13 | 20/07/2021 | No | No | |
| Preprint results | 24/01/2022 | 19/07/2022 | No | No | |
| Results article | 03/11/2022 | 08/04/2024 | Yes | No |
Additional files
- ISRCTN16013277_PROTOCOL_v1.8_03Mar20.pdf
- Uploaded 06/03/2020
- ISRCTN16013277_PROTOCOL_02Jul20_v1.9.pdf
- Uploaded 02/07/2020
- ISRCTN16013277_SAP_v12_30Jun2021.pdf
- Uploaded 05/07/2021
- ISRCTN16013277_SAP_V13.pdf
Editorial Notes
08/04/2024: Publication reference added.
19/07/2022: Added link to preprint.
12/04/2022: The following changes were made to the trial record:
1. The recruitment start date was changed from 16/03/2020 to 06/07/2020.
2. The recruitment end date was changed from 27/04/2021 to 27/04/2021.
3. The overall trial end date was changed from 30/06/2021 to 24/06/2021.
4. The intention to publish date was changed from 31/12/2021 to 30/04/2022.
20/07/2021: Uploaded statistical analysis plan Version 13.
05/07/2021: Uploaded statistical analysis plan Version 12.
15/06/2021: The following changes have been made:
1. The recruitment end date has been changed from 30/06/2021 to 27/04/2021.
2. The total final enrolment number has been added.
02/07/2020: Recruitment to this study is no longer paused. Uploaded protocol Version 1.9, 2 July 2020 (not peer reviewed)
17/04/2020: Due to current public health guidance, recruitment for this study has been paused.
06/03/2020: Trial's existence confirmed by Cambridge Psychology Research Ethics Committee. Uploaded protocol Version 1.8, 3 March 2020 (not peer reviewed)
