Optimizing Chatbot Reminder Timing in a Chatbot Cessation Service: A Micro-Randomized Trial

NCT07826884 | Recruiting DMC

• 1 other identifier: Chat to Quit_MRT
• Study Type: interventional
• Target: 350
• Locations: 1 country
• Sites: 1

Brief Summary

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.

Conditions

Smoking Cessation

Keywords

Smoking cessation; Behavioral counselling; Digital health; Artificial intelligence; Chatbot; Engagement; Push notification

Outcome Measures

Primary Outcomes (1)

• 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.

  Within 24 hours after each randomized reminder delivery during the 12-week chatbot cessation service period

Secondary Outcomes (3)

• Any chatbot reply within 24 hours after reminder delivery

  Within 24 hours after each randomized reminder delivery during the 12-week chatbot cessation service period

• Response latency after reminder delivery

  Within 72 hours after each randomized reminder delivery during the 12-week chatbot cessation service period

• Extended meaningful engagement with chatbot after reminder delivery

  Within 48 and 72 hours after each randomized reminder delivery during the 12-week chatbot cessation service period

Study Arms (1)

Chatbot Cessation Service With Randomized Reminder Timing

EXPERIMENTAL

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

Interventions

Chatbot Cessation Service With Randomized Reminder Timing BEHAVIORAL

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.

Chatbot Cessation Service With Randomized Reminder Timing

Eligibility Criteria

• Sex: all
• Healthy Volunteers: No
• Age Groups: Child (0-17), Adult (18-64), Older Adult (65+)

You may qualify if:

• 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))

You may not qualify if:

• Have communication difficulties (either physical or cognitive) that prevent completion of the counselling and assessments
• Having queries irrelevant to tobacco control

Sponsors & Collaborators

• The University of Hong Kong: lead

Study Sites (1)

School of Nursing, The University of Hong Kong

Hong Kong, Hong Kong

RECRUITING

MeSH Terms

Conditions

Smoking Cessation

Condition Hierarchy (Ancestors)

Health Behavior; Behavior

Central Study Contacts

Man Ping Wang

CONTACT

+852 3917 6636; mpwang@hku.hk

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: NA
• Masking: NONE
• Purpose: HEALTH SERVICES RESEARCH
• Intervention Model: SINGLE GROUP
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Professor

Model Details: An embedded micro-randomized trial within the chatbot cessation service. Participants will remain in a single chatbot cessation service cohort and will be repeatedly randomized at each weekly decision point to receive scheduled reminders delivered under predefined day-type (weekday/weekend) and time-of-day (morning/afternoon/evening) conditions during the 12-week chatbot cessation service period.

Study Record Dates

• First Submitted: September 11, 2026
• First Posted: September 17, 2026
• Study Start: September 28, 2026
• Primary Completion (Estimated): October 31, 2027
• Study Completion (Estimated): December 31, 2027
• Last Updated: October 1, 2026

Record last verified: 2026-09

Data Sharing

• IPD Sharing: Will not share

Locations

HK (1)