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.
Able to communicate in Chinese (Cantonese)
Have access to or are willing to use WhatsApp to access the chatbot cessation service
Used any tobacco in the past 30 days (including all types of tobacco products such as cigarette, shisha, electronic cigarettes, and heat-not-burn (HNB))
Have communication difficulties (either physical or cognitive) that prevent completion of the counselling and assessments
Having queries irrelevant to tobacco control
Single group
Chatbot Cessation Service With Randomized Reminder Timing
BehavioralThe 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.
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.
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.
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.
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