Efficacy of personalised text message intervention in reducing smoking frequency and amount for non-abstinent smokers: A double-blind, randomised controlled trial

Background Emerging evidence supports the efficacy of mobile phone interven-tions for smoking cessation. However, behaviour changes of smokers who fail to reach abstinence and the related psychological mechanism are still understudied. We aimed to evaluate the efficacy of a behaviour change theory-based smoking cessation intervention delivered through personalised text messages from the per-spective of smokers who fail to reach abstinence. Methods We conducted a two-arm, double-blind, randomised controlled trial, with the intervention group receiving personalised text messages developed spe-cifically for this study, and the control group receiving non-personalised ones related to smoking cessation. These messages were sent over a period of three months. We looked at three outcomes: changes in smoking frequency, in smoking amount, and in protection motivation theory (PMT) construct scores. Results We obtained smoking cessation results for 722 participants who went through the randomisation process (intervention: 360, control: 362; block ran-domisation design). Overall, 32.3% of baseline daily smokers in the intervention group and 20.0% in the control group changed to weekly smokers during the fol-low-up period (P < 0.001), while 43.4% of consistent daily smokers in the inter-vention group and 32.8% in the control group continuously reduced their smok-ing amount (P < 0.001). We observed associations between the intrinsic rewards of smoking and changes from daily to weekly smoking, the perceived severity of smoking and reductions in smoking amount, as well as the self-efficacy of quit-ting and changes from daily to weekly smoking/reductions in smoking amount. Conclusions We found that a personalised text message-based intervention was more likely to decrease the frequency and amount of smoking in smokers who failed to reach abstinence compared to a non-personalised one. We also explored the possible psychological mechanism of such positive effects. Here we provide evidence for countries to consider the promotion of smoking cessations using be-haviour theory-driven personalised text messages, which may be more cost-effec-tive than traditional approaches.