The goal of this factorial trail is to to optimize an intervention package to enhance quit attempt preparations, quit attempts, and tobacco abstinence among smokers without a plan to quit.

The main questions it aims to answer are:

• What are the main effects of the four intervention components for increasing quit attempt preparation?
• Are there synergistic or antagonistic interactions between components?
• Does chat-based instant message or chatbot enhance the effects of nicotine replacement therapy sampling and/or simple exercise education in increasing motivation to quit?
• When participants experienced successful quitting by using the nicotine replacement therapy patch, will other tools, such as simple exercise education, chat-based instant messages, or chatbot, could help in the process and strengthen the effects of the nicotine replacement therapy patch and solve the possible problems they may encounter in using nicotine replacement therapy patch in a timely manner?

1. Aims of the project This proposed project aims to optimize an intervention package to enhance quit attempt preparations, quit attempts and tobacco abstinence among smokers without a plan to quit. We expect that this study's results would demonstrate the different main effects of physical, pharmaceutical, and psychological components and their synergistic effects on smoking cessation induction. With the revealing of different effects of individual or synergistic effects of these four intervention components, including simple exercise education, NRTS, CBIM and chatbot, future smoking cessation programs may have a more precise design of using which combinations to motivate smokers. This study will also prepare for future RCTs to explore the efficacy of single or synergistically intervention components/factors for promoting smoking cessation induction. In the long run, the proportion of intervention in quit attempts and preparation to quit would increase and meet the international level and, therefore, speed up declining smoking prevalence to a single digit.

2. Study design A pilot balanced full factorial design with four components/factors: 1) SEE versus none; 2) NRTS versus none; 3) CBIM versus none; and 4) chatbot for smoking cessation versus none, and to 2 x 2 x 2 x 2=16 trial groups. All participants will be randomly and evenly assigned to these 16 intervention groups. This study protocol complies with Declaration of Helsinki and International Conference on Harmonisation Guideline for Good Clinical Practice (ICH-GCP).

3. Subjects Inclusion criteria will include 1) being a Hong Kong resident aged ≥18 years; 2) using any tobacco products every day; 3) having WhatsApp installed on their cell phone; 4) no injuries in hands and arms; 5) no medical contraindications to NRT (no severe angina, serious cardiac arrhythmias and hypertension); and 6) no plan to quit in the next 30 days. Exclusion criteria will include smokers who 1) cannot communicate in Cantonese or read Chinese; 2) currently using smoking cessation services and medication; 3) self-reported psychosis, bipolar disorder, or on psychiatric medication; and 4) pregnant smokers. As this is a pilot study to test the feasibility of conducting a full factorial design, we will recruit (10 participants x 16 groups) 160 participants to enroll in this study.

4. Recruitment strategy In the outdoor recruitment sessions, the recruitment staff will approach and distribute souvenirs or leaflets to the smokers who are smoking for 3-4 hours in the daytime. If a smoker is willing to accept them and talk to the recruitment staff, the staff will introduce the study, invite them to consent for participation, and complete a simple baseline questionnaire for further contacts and intervention delivery. Participants who complete the enrolment procedures will be offered a HKD50 shopping voucher to compensate their time spent. We will conduct 3 follow-up calls. They will be conducted after 1 week, 1 month and 3 months. In the 1 month and 3 months follow-up calls, if the participants claim s/he has already quitted smoking for equal to or more than 7 days, we will test the carbon monoxide and codinine level. Since smokers normally have higher levels of cotinine and carbon monoxide levels, we could prove if s/he quit smoking or not. We will implement carbon monoxide detector to check the carbon monoxide level, while cotinine will be used to test the cotinine level in the saliva.

5. Intervention Factor 1: Simple exercise education (SEE) All participants will be given a handgrip at study enrolment. The SEE includes a Zoom/WhatsApp meeting or face-to-face session including 1) watching a 5-minute video (www.youtube.com/watch?v=mZex2Wwy3fU) showing a chair professor of public health demonstrating the 10s-E, including the simple exercises with and without handgrip. The video also encourages participants to 1) follow the exercise instructions during the video demonstration; 2) perform the exercises whenever they experience craving or an urge to smoke during the quitting process; and 3) increase their exercise frequency and intensity as much as possible, which may also increase their grip strength. Participants will also receive a leaflet with exercise instructions and motivational messages.

   Factor 2: NRT sampling The intervention includes a Zoom/WhatsApp meeting or face-to-face session, where a trained counsellor will introduce the instruction of NRT use and possible side effects to the participant based on an intervention guide we used in the previous RCT of NRTS. The trained counsellor will suggest the NRT patch's dosage based on his/her daily cigarette consumption. If the intervention is delivered online, an intervention pack including a pamphlet and 1-week free NRT sample (patch: 14mg or 21mg) will be mailed to the participants. At 1-week after sending the NRT, the trained counsellor will follow-up with the participant. If the participant has completed all patches and willing to use more, the counsellor will mail 1 additional pack of NRT to him/her and ask him/her to obtain more from the current smoking cessation service or purchase in pharmacy. Users of NRT patch may experience skin reactions, insomnia and/or vivid dreams. If participants experience severe side effects of NRT use, the counsellor will ask them to cease use.

   Factor 3: Chat-based instant messaging Participants will receive individualized chat-based encouragement and support messages about motivation and preparation for quit attempts using WhatsApp for 8 weeks. A trained smoking cessation counsellor will have real-time (synchronous), one-to-one interaction with the participants and provide personalized motivational, behavioural support according to the participants' needs. The conversation intensity will be flexible and depend on the participant. The conversation will also be integrated with brief advice using the Behaviour Change Techniques (BCTs) (18) and the AWARD (Ask, Warn, Advise, Refer, Do-it-again) intervention model (11). The intervention protocol will be similar as that in our previous RCT on CBIM (19). For participants who receive the SEE and NRTS, the trained counsellor shall follow-up on their compliance and provide adequate advice in adhering to these interventions.

   Factor 4: Chatbot for smoking cessation The information and access to the chatbot will be introduced to participants. Through the chatbot service, participants shall access to practical information on smoking cessation 24 hours at any time, such as details on cessation services and skills for tackling cravings. By using the second-generation chatbot, participants could receive personalized risk information and recommendations for smoking cessation, as well as reach to a counsellor through WhatsApp live chat for urgently needed advice.

6. Randomization, allocation concealment and blinding The random allocation sequence will be computer-generated by an investigator who has no other involvement in the study. Simple individual randomization by sequentially numbered, opaque sealed envelopes (SNOSE) will be used to ensure the recruitment staff and the participants will be concealed in the allocation sequence before the group allocation.

   Blinding of participants and the research staff who deliver the intervention will not be possible. Follow-up outcome assessments will be conducted by research assistants who will be blinded for the group allocation.

7. Evaluation plan To examine whether the intervention can be delivered as it is designed (scalability), we will evaluate the intervention fidelity and smokers' adherence to the intervention. Regarding to SEE, counsellors will document the time spent on delivering the SEE and participants' response. Regarding NRTS, counsellors will document the time spent on medication advice, what will be included in the advice, and any side effects or concerns reported by the participants at 1-week follow-up. Regarding CBIM, number of messages sent by counsellors and the participants will be documented. For chatbot, number of messages sent by participants will be recorded.

8. Data analyses All statistical analysis will be conducted in STATA/MP version 16.1. The primary analysis will examine the intervention's main and interaction effects on the primary outcome by intention-to-treat, assuming non-respondents at follow-up are smokers without quit attempts. Between-subject factorial linear mixed model (LMM) will be used to evaluate the main effects, six 2-way interactions (SEE X NRTS, SEE X CBIM, NRTS X CBIM, SEE X chatbot, NRTS X chatbot, CBIM X chatbot), four 3-way interaction (SEE X NRT X CBIM, SEE X NRT X chatbot, SEE X CBIM X chatbot and NRT X CBIM X chatbot) and one 4-way interaction (SEE X NRTS X CBIM x chatbot) using effect coding (levels are coded -1 and +1) on IBC-S. Analyses will be adjusted for demographics and smoking-related covariates, and supplemented with multiple imputation and complete-case analysis. The IBC-S score of sub-groups involved in a significant interaction (5% level of significance) will be plotted on a bar chart to visualize the comparisons.

9. Direct access to source data/documents The raw data will be stored in the CD-ROM and locked in a cupboard with keys kept by the Principal Investigator. Only the Investigators and Research Assistants of the project will be permitted access to raw data and/or study records. The data will be kept for 10 years after the study is completed.

10. Dissemination of study result The initial findings will be submitted for application for the coming round of the Health Medical Research Fund or the General Research Fund. The findings will be disseminated through publication in the journal Addiction or other peer-reviewed journals. Also, the findings will be useful evidence for expert comments or deputations of smoking-related issues in the Legislation Council.

11. Consent Eligible participants will be invited to participate in the study by obtaining written consent.

Inclusion Criteria:

• Being a Hong Kong resident aged ≥18 years;
• Using any tobacco products every day;
• Having WhatsApp installed on their cell phone;
• No injuries in hands and arms;
• No medical contraindications to NRT (no severe angina, serious cardiac arrhythmias and hypertension); and
• No plan to quit in the next 30 days.

Exclusion Criteria:

• Cannot communicate in Cantonese or read Chinese;
• Currently using smoking cessation services and medication;
• Self-reported psychosis, bipolar disorder, or on psychiatric medication; and
• Pregnant smokers.

Research data and documentation will be available upon request

3 years after the completion of the relevant publications