Mobile instant messaging supported brief physical exercise intervention for smoking cessation: a community-based, cluster randomised controlled trial

INTRODUCTION: Physical exercise has been used to assist smoking cessation, but supervised programmes are bounded by limited scalability and generalisability. Mobile instant messaging (MIM) offers a scalable platform for delivering exercise support with minimal supervision. We assessed the effectiveness of MIM-supported brief physical exercise intervention on smoking cessation. METHODS: In this two-arm, parallel, cluster randomised controlled trial, we recruited daily smokers aged 18 years or older from 70 community sites in Hong Kong from June to October 2022. Sites were randomised (1:1) to either the intervention group (n=492) or control group (n=539). Brief cessation advice, physical exercise instructions and MIM-based practice reminders were offered to the intervention group for 3 months. The primary outcome was biochemically validated 7-day point prevalence abstinence (PPA) at 6 months. RESULTS: Of the 1031 participants (80.9% male, mean age 44.2 years), 59.8% were followed up at 6 months. Biochemically validated abstinence rates at 6 months were non-significantly higher in the intervention than the control group (10.4% vs 9.1%; risk ratio (RR) 1.14, 95% CI 0.79 to 1.66, p=0.48). Self-reported 7-day PPA was 21.9% and 19.5%, respectively (RR 1.13, 95% CI 0.89 to 1.43, p=0.32). Weekly practice of handgrip and elastic band exercises in the intervention group declined significantly over 6 months (from 10.3 min to 2.5 min and from 9.4 min to 0.8 min; p