Discussion
BLIND
This study joins the recent debate on mobile phone-based cessation interventions and provides some new information. The intervention group receiving personalized text messages about smoking cessation based on behaviour change theory had a 6-month quitting rate that was twice that of the intervention group getting non-personalized messages. We found that messages designed to counteract the intrinsic rewards of smoking was one of the important variables associated with sustained abstinence. Examples of intrinsic rewards include: “Smoking makes me feel comfortable”, “Smoking helps me concentrate” or “Smoking enhances brainwork”. In contrast, extrinsic rewards may be less important in influencing this behaviour. Examples include “Smoking looks cool and fashionable”, “Smoking is good for social networking” or “The life of a smoker is happier than that of a non-smoker”. This association has been confirmed by other studies in China.The comparison between groups shows that the personalized intervention decreased the intrinsic rewards of smoking and the response cost of quitting; this finding is worth noting, as both are determinants of long-term abstinence. This finding also provides some indications of why the intervention group had better results than the control group and provides further guidance for scaling up our intervention.This study has several limitations. First, although we made efforts to ensure that both the researchers and participants remained blind to the allocation, the blinding may have been broken during multiple face-to-face contacts. Second, expired air carbon monoxide testing is the common method of detecting recent smoking and is recommended as a standard for the assessment of smoking cessation in trials. However, these biochemical tests are not perfect; expired air carbon monoxide can only be detected for approximately 24 hours after tobacco use. Third, the scale we used to evaluate protection motivation theory components was the same at each follow-up visit, and some participants may have remembered some of the questions and provided inaccurate answers. Fourth, there were only six female smokers in the cohort. Therefore, the situation among female smokers may not be fully represented when interpreting these results. Fifth, we only investigated the effects of the intervention for 6 months. We therefore do not know if anyone changed their smoking habits after 6 months. Sixth, the profile of our intervention consisted of one or two messages a day. We have no idea of what the effect would have been if a more extensive intervention were used, so we could not have a measure of what we might consider an optimal level of intervention. Seventh, some participants may live in the same community or have close contact. There was a risk of sharing messages with other participants. This could have biased our results.Despite these limitations, our study has theoretical and policy implications. First, mobile phone-based cessation studies often suffer from insufficient reporting of the principles, and our study provides a full description of the intervention with a clear framework that can allow other researchers to take advantage of our experience. Second, we identified the psychological determinants of long-term abstinence that can allow future smoking cessation interventions to focus more on those points. However, researchers should not ignore other components of the protection motivation theory. For example, why did other variables, such as extrinsic rewards and response efficacy, show a relatively weak association with long-term abstinence? How do those variables contribute to changing smoking behaviour to achieve sustained abstinence? These questions have strong theoretical implications and need to be studied further.Our findings suggest that the intervention we used in this study is acceptable and effective for adult smokers, without the need for additional resources, and no major challenges were encountered. It might be suitable for use in other settings with limited smoking cessation resources. The message and skills used in this intervention are not closely related to any cultural background; therefore, it might technically be easy to implement in other settings or countries with different cultural backgrounds or to target other health behaviours. The personalized evaluation tools disseminated via WeChat are also easily achieved by other online chatting tools or applications at a low cost.This personalized text message intervention increased the rate of biochemically veriﬁed smoking cessation at 6 months. China has the world’s largest number of smokers but has inadequate resources to provide cessation services via medical institutions. If this intervention is scaled up nationwide and again demonstrated to be effective, it may benefit smokers, particularly in rural areas.