Mobile Chat Messaging for Smoking Relapse Prevention: A Randomized Clinical Trial.

Importance: Most individuals attempting smoking cessation relapse, even with evidence-based treatment. Mobile interventions offer a potential but largely untested strategy to sustain cessation. Objective: To test the effectiveness of mobile chat messaging for relapse prevention among individuals who recently quit smoking. Design, Setting, and Participants: This randomized clinical trial was conducted from March 14, 2023, to August 15, 2024, at 2 clinic-based smoking cessation services in Hong Kong. Participants were adults who smoked daily and had abstained for 3 to 30 days; they were randomly assigned to an intervention group or a control group. Interventions: All participants received usual smoking cessation treatment from the services. The intervention group additionally received 3 months of mobile relapse prevention intervention, including chat-based support delivered by a live counselor and access to a supportive chatbot via a messaging app. The control group received 8 text messages on generic smoking cessation advice over 3 months as a contact control. Main Outcomes and Measures: The primary outcome was biochemically validated tobacco abstinence at 6 months after randomization, defined by an exhaled carbon monoxide level of less than 5 ppm or a negative salivary cotinine test result. Secondary outcomes at 6 months included self-reported prolonged abstinence, 7-day point prevalence abstinence, and relapse (7 consecutive days of smoking) rate. Intention-to-treat analyses were conducted, assuming participants with missing outcomes relapsed. Results: Of 590 participants, 465 (78.8%) were male, and the mean (SD) age was 47.1 (11.2) years; 294 were randomized to the intervention group and 296 were randomized to the control group. The retention rate at 6-month follow-up was 98.0% (n = 578). Biochemically validated abstinence at 6 months was significantly higher in the intervention group than in the control group (45.9% [135 of 294] vs 35.5% [105 of 296]; relative risk [RR], 1.29; 95% CI, 1.06-1.58; P = .01). The intervention group also reported significantly higher prolonged abstinence (57.5% [169 of 294] vs 47.6% [141 of 296]; RR, 1.21; 95% CI, 1.03-1.41; P = .02), higher 7-day point prevalence abstinence (65.6% [193 of 294] vs 54.7% [162 of 296]; RR, 1.20; 95% CI, 1.05-1.37; P = .007), and lower relapse rate (33.0% [97 of 294] vs 44.9% [133 of 296]; RR, 0.73; 95% CI, 0.60-0.90; P = .003) at 6 months. Conclusions and Relevance: This randomized clinical trial found that mobile chat messaging for smoking relapse prevention increased validated abstinence by approximately 30%, offering a scalable approach to sustain abstinence among individuals who recently quit smoking. Trial Registration: ClinicalTrials.gov Identifier: NCT05370352.