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

September 16, 2026 updated by: Prof. Wang Man-Ping, The University of Hong Kong

A Micro-Randomized Trial to Optimize the Timing of Weekly Chatbot Reminders for User Engagement in a Chatbot Cessation Service

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.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Not yet recruiting

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Detailed Description

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.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Estimated)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
350

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.
  • Name: Man Ping Wang
  • Phone Number: +852 3917 6636
  • Email: mpwang@hku.hk

Study Locations

  • Hong Kong
      • Hong Kong, Hong Kong
        • School of Nursing, The University of Hong Kong
        • Contact:
          • Man Ping Wang
          • Phone Number: +852 3917 6636
          • Email: mpwang@hku.hk

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

  • Child
  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • 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))

Exclusion Criteria:

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

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Health Services Research
  • Allocation: N/A
  • Interventional Model: Single Group Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: Chatbot Cessation Service With Randomized Reminder Timing
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.

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
Meaningful engagement with chatbot within 24 hours after reminder delivery
Time Frame: Within 24 hours after each randomized reminder delivery during the 12-week chatbot cessation service period
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 Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Any chatbot reply within 24 hours after reminder delivery
Time Frame: Within 24 hours after each randomized reminder delivery during the 12-week chatbot cessation service period
Whether participants provide any reply to the chatbot after receiving a randomized weekly reminder, as recorded by the chatbot system.
Within 24 hours after each randomized reminder delivery during the 12-week chatbot cessation service period
Response latency after reminder delivery
Time Frame: Within 72 hours after each randomized reminder delivery during the 12-week chatbot cessation service period
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.
Within 72 hours after each randomized reminder delivery during the 12-week chatbot cessation service period
Extended meaningful engagement with chatbot after reminder delivery
Time Frame: Within 48 and 72 hours after each randomized reminder delivery during the 12-week chatbot cessation service period
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.
Within 48 and 72 hours after each randomized reminder delivery during the 12-week chatbot cessation service period

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
The University of Hong Kong

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
September 28, 2026

Primary Completion (Estimated)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
October 31, 2027

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
December 31, 2027

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
September 11, 2026

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
September 16, 2026

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
September 17, 2026

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
September 17, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
September 16, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
September 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • Chat to Quit_MRT

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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