Chat-based instant messaging support with optional combined interventions for Chinese community smokers in Hong Kong: Preliminary analysis of a sequential, multiple assignment, randomized controlled trial (SMART)

Introduction: Chat-based support (CBS) via instant messaging was effective in doubling quit rate. But smokers with a low intention to quit may need interventions that can meet their individualized needs. Objectives: To test the effect of CBS integrated with optional combined interventions (OCI) on quitting using SMART. Methods: Proactively recruited adult daily smokers to receive brief advice and actively referred to smoking cessation services were conducted from June to September 2019. Participants were individually randomized to receive CBS (Intervention group) or regular instant messages (RIM, Control group). Smoking status was assessed at 1-month and smoking participants were randomized for adaptive interventions. Smoking participants in the Intervention group were randomized to receive OCI, including phone counselling (PC), multi-media messages (MMM), nicotine replacement therapy sampling (NRT-S), financial incentive for active referral (FIAR), and family/peer support group chat (SGC). Smoking participants in the Control group were randomized to receive CBS. Quitters in both groups received the initial intervention. The primary outcomes were biochemically validated abstinence at 3- and 6-month. Intention-to-treat analyses were adopted. Results: A total of 844 participants (82.4% men, 65.3% aged 30-59) were randomized (each group 422). Participants smoked 13.9 cigarettes per day on average and 45.2% had no intention to quit within 30 days. We expect to complete the 6-month follow-up in Apr 2020. The retention rate at 1-month was 78.6%. Preliminary results revealed similar quit rates in two groups at 1-month (12.8% vs. 11.8%, p=0.66). Smoking participants (n=368) in the Intervention group were randomized for OCI (n=271) or continuing CBS (n=97) at a ratio of 3:1. Among OCI participants, 55.4% chose PC, 50.2% chose MMM, 30.6% chose NRT-S, 10.7% chose FIAR and 0.4% chose SGC. Smoking participants (n=372) in the Control group were randomized for CBS (n=91) or continuing RIM (n=281). Conclusion(s): This study will inform the development of adaptive interventions for smoking cessation.