An interventional study of Chatbot Cessation Service With Randomized Reminder Timing in Smoking Cessation, sponsored by The University of Hong Kong. Recruiting at 1 site in Hong Kong. Per ClinicalTrials.gov, last updated 2026-10-01.
Sponsored by The University of Hong Kong · Not applicable, Interventional, and Health services research
The goal of this study is to learn whether the timing of weekly chatbot reminders affects user engagement with the chatbot cessation service. Participants enrolled in the routine chatbot cessation service will be included in a micro-randomized trial. The delivery timing of weekly reminders will be randomly assigned across different day types and times of day during the 12-week chatbot cessation service period. The study will use routine chatbot system records to evaluate engagement after reminder delivery, including whether participants respond to the chatbot and how quickly they re-engage with the service.
Sustained user engagement remains a challenge in digital smoking cessation interventions. In this chatbot cessation service, routine weekly AI-generated reminders are used to encourage users to re-engage with chatbot-based smoking cessation support during the 12-week service period. However, the optimal timing for delivering these reminders remains uncertain. This study is an embedded micro-randomized trial conducted within the existing chatbot cessation service. The aim of this study is to evaluate whether the timing of weekly chatbot reminders influences short-term user engagement and to identify optimal reminder delivery schedules. Participants enrolled in the routine chatbot cessation service will be included in the micro-randomized trial through an opt-out approach. The trial will not introduce any additional intervention components, measurements, or study visits beyond the existing chatbot cessation service and follow-up assessments. Participation in the micro-randomized trial will only affect the timing of routine weekly reminders. During the 12-week chatbot cessation service period, excluding the initial welcoming message, the delivery timing of 11 weekly reminders will be randomized across predefined day-type and time-of-day conditions. Reminder strategy will remain unchanged. The primary proximal outcome is meaningful engagement with the chatbot within 24 hours after reminder delivery, as recorded by the chatbot system. Secondary outcomes include reply status, response latency, and meaningful engagement within 48 and 72 hours after reminder delivery. Meaningful engagement is defined as user messages relevant to smoking cessaation. The findings from this study will provide evidence to optimize the timing of routine chatbot reminders and inform future development of optimized reminder strategies and adaptive digital smoking cessation interventions.
1,581 studies on the registry are indexed under Smoking Cessation; 198 are open to participants now.
This study's planned enrollment of 350 is above the median of 164 across 1,423 interventional studies indexed under Smoking Cessation.
Browse Smoking Cessation studies →The University of Hong Kong is the lead sponsor of 1,292 studies on the registry; 348 are open to participants now.
Of its 9 completed or terminated interventional studies of FDA-regulated products, 0 (0%) have results posted.
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Exclusion Criteria:
Participants will receive the routine chatbot-based smoking cessation service for 12 weeks. Within the service, the delivery timing of weekly chatbot reminders will be repeatedly randomized at weekly decision points across predefined day-type and time-of-day conditions using a micro-randomized trial design. The reminder content and chatbot support provided to participants will remain consistent.
Behavioral: Chatbot Cessation Service With Randomized Reminder Timing
The chatbot cessation service provides digital smoking cessation support through a chatbot platform. Participants receive routine chatbot-based cessation support, including scheduled weekly AI-generated reminders during the 12-week service period. Excluding the initial welcoming message, the timing of the remaining 11 weekly reminders will be repeatedly randomized at weekly decision points across predefined day-type and time-of-day conditions. The randomized component is limited to reminder delivery timing. All participants receive the same chatbot content and support.
Meaningful engagement with chatbot within 24 hours after reminder delivery
Meaningful engagement is defined as any reply regarding smoking cessation excluding emoji and simple message like "Hi" within 24 hours after receiving a randomized weekly reminder. Engagement will be automatically recorded by the chatbot system.
Time frame: Within 24 hours after each randomized reminder delivery during the 12-week chatbot cessation service period
Any chatbot reply within 24 hours after reminder delivery
Whether participants provide any reply to the chatbot after receiving a randomized weekly reminder, as recorded by the chatbot system.
Time frame: Within 24 hours after each randomized reminder delivery during the 12-week chatbot cessation service period
Response latency after reminder delivery
The time interval between randomized reminder delivery and the participant's first reply to the chatbot within 72 hours after reminder delivery, as recorded by the chatbot system.
Time frame: Within 72 hours after each randomized reminder delivery during the 12-week chatbot cessation service period
Extended meaningful engagement with chatbot after reminder delivery
Meaningful engagement is defined as any reply regarding smoking cessation excluding emoji and simple message like "Hi" within 48 and 72 hours after receiving a randomized weekly reminder. Engagement will be automatically recorded by the chatbot system.
Time frame: Within 48 and 72 hours after each randomized reminder delivery during the 12-week chatbot cessation service period
Plan to share: No
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