Smoking cessation (SC) interventions using behavioral economics mainly focus on financial incentives, which were used to change health behaviors by utilizing a reward system to enhance long-term maintenance. Incentives have been demonstrated to enhance SC across various populations with moderate effects. Interventions for smoking cessation characterized by financial incentives focus primarily on the potential for monetary gain rather than loss. Changing the motivational strategy to combine disclosing losses with providing financial incentives may increase the effectiveness of financial consequence-based smoking cessation interventions. Thus, this study aims to test, by a 2-arm RCT, the effectiveness of an intervention of which includes mobile phone-based intervention combined with small incentive and smoking cessation in workplaces in Hong Kong; identify facilitators and barriers of successful policy implementation and quitting; examine and evaluate the company environment and their policies in promoting smoking cessation.

This study will separate into two phases. Phase I is a large scale cross-sectional survey of corporations in Hong Kong to examine the employers' knowledge, attitudes and practices in promoting SC in the workplace. Phase II is a 2-arm randomized controlled trial that will be conducted to examine the effectiveness of mobile phone-based intervention combined with company health talk, brief phone counselling and nicotine replacement therapy sampling, for SC in workplaces.

Data analyses Phase I: Descriptive statistics will be used to analyze the (1) profile of the corporations, including the total number of employees and smoking employees; (2) employers/managerial staff's knowledge on smoking; (3) employers/managerial staff's attitudes on smoking cessation; (4) practices of the companies with respect to smoking cessation.

Phase II: Primary outcome is self-reported abstinence in the past 7 days at 6-month follow-up. Secondary outcomes for smoking cessation include self-reported abstinence in the past 7 days at 9- and 12-month follow-ups, the biochemically validated abstinence (defined as exhaled CO level <4ppm and saliva cotinine level ≤30 ng/ml); smoking reduction (50% or above reduction in cigarette consumption compared with baseline. Secondary outcomes for mental health include stress (Perceived Stress Scale-10), depression (Personal Health Questionnaire for Depression), anxiety (Generalized Anxiety Disorder scale) and self-rated health.

Descriptive statistics such as frequency, percentage, and mean will be used to summarize the outcomes and other variables. Chi-square tests and t-tests will be used to compare outcome variables between subgroups. The intention-to-treat (ITT) analysis will be used such that those lost to contact and refused cases at the follow-ups will be treated as no reduction in cigarette consumption nor quitting. Multiple imputations will be used to compute missing data for outcome variables. The association between intervention adherence (e.g., engagement in the IM interaction) and the primary outcome within the participants in the intervention group will be examined. The intervention effect by subgroups will be assessed respectively, including sex, age, education level, company types, previous quit attempts, cigarette dependence, and intention to quit, although the statistical power would be lower due to smaller numbers.

Inclusion Criteria:

1. Hong Kong residents aged 18 or above
2. Current smoking cigarettes or alternative tobacco products daily with an exhaled carbon monoxide level ≥4 ppm or a positive salivary cotinine test
3. Able to communicate in Cantonese/Mandarin and read Chinese
4. Able to use instant messaging tool (e.g. WhatsApp) for communication.
5. Stay in Hong Kong during the intervention and follow-up periods (12 months)

Exclusion Criteria:

1. Smokers who are psychologically or physically unable to communicate
2. Currently following other SC program(s)
3. Having used NRT for the past month
4. Having severe angina, serious cardiac arrhythmias and hypertension
5. Have acute myocardial event in the past month
6. Being pregnant or providing breastfeeding