Introduction
PMT
Smoking kills more than 1 million people in mainland China every year, and the number is predicted to grow to 2 million by 2030 and 3 million by 2050 [A large number of studies have shown that mobile cessation interventions can improve the smoking cessation rate and have the potential to provide smoking cessation services broadly, but most previous studies have focused only on the quitting rate [Another dimension is the determinant of quitting behavior. Several recent studies have noted that some factors could be associated with short-term or long-term abstinence [To help fill this evidence gap, we conducted a randomized controlled trial (RCT) to provide valuable evidence on these topics. We found that a personalized and behavior change theory–based SMS text message smoking cessation intervention was more effective than a nonpersonalized SMS text message intervention (6.9% vs 3.0%; adjusted odds ratio [OR] 2.66, 95% CI 1.21-5.83). The effectiveness of our intervention has been reported in The purpose of this study was to evaluate the changes in protection motivation theory (PMT) subconstructs and the transtheoretical model (TTM) stages of change to provide insight into why a personalized mobile cessation intervention was more likely to promote smokers from the preparation stage to the action stage. To our knowledge, this study is the first RCT using personalized SMS text messages for a mobile cessation intervention with a positive control group design in a country with a limited tobacco control policy.The TTM has been widely used for health behavior change interventions. The theory identifies five stages of change: precontemplation, contemplation, preparation, action, and maintenance. It is an integrative behavior change model for intentional change focused on the decision-making of individuals. Given the systematic relationship between the stages and processes of change, several strategies have been used to strengthen behavior changes or to achieve the next stage [Many studies have found that personalized and behavior change theory–based interventions could be more effective than only providing broad, nonspecific advice [Our previous research used cross-sectional data and found that smokers have different psychological factors that influence their quitting intention or behavior [