Social and Monetary Incentives for Smoking Cessation at Large Employers
Phase: NA
Conditions: Tobacco Use Disorder
Sponsor: University of California, Berkeley

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Social and Monetary Incentives for Smoking Cessation at    
Large Employers 
(SMILE Study) 
 
 
Study Protocol 
 
 
Principal Investigator:  
William H. Dow, PhD, University of California at Berkeley 
 
Supported by:  
The National Institutes of Health 
Grant: R01-DA035384 
 
Registered with: 
www.ClinicalTrials.gov  
Identifier: NCT02421224 
 
Approved by: 
University of California at Berkeley Institutional Review Board 
IRB #: 2012-11-4792 
 
Mahidol University  
Protocol Number 2014/1-1-06 
 
Draft or Version Number: 2.2 
 
Date Last Revised: April 29, 2019 
 
 
 

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Table of Contents 
 
A. 
Key roles and contact information ..................................................................................... 3 
B. 
Background and rationale .................................................................................................. 4 
1. 
Background ................................................................................................................. 4 
2. 
Rationale .................................................................................................................... 7 
C. 
Study objectives ................................................................................................................. 7 
D. 
Study design ....................................................................................................................... 8 
1. 
Study population ........................................................................................................ 8 
2. 
Recruitment ................................................................................................................ 9 
3. 
Interventions ............................................................................................................ 10 
4. 
Study procedures ...................................................................................................... 12 
5. 
Randomization ......................................................................................................... 16 
6. 
Outcomes ................................................................................................................. 17 
7. 
Data management .................................................................................................... 17 
8. 
Statistical considerations .......................................................................................... 18 
E. 
Literature Cited ................................................................................................................ 19 
 
 

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A. Key roles and contact information 
 
Principal Investigator: 
 
William H. Dow, PhD 
University of California at Berkeley 
School of Public Health 
Tel: 510-643-5439 
wdow@berkeley.edu 
 
Site Principal Investigator: 
 
Aree Jampaklay, PhD 
Mahidol University 
Institute for Population and Social Research 
999 Phuttamonthon 4th Road, Phutthamonthon 
Salaya, Nakhon Pathom 73170, Thailand 
Tel: +66 2441-0201-4 ext. 501 
aree.ude@mahidol.ac.th 
 
Other Key Personnel: 
 
Justin S. White, PhD 
University of California, San Francisco  
Box #0936 
San Francisco, CA 94143 
tel: 1-415-476-8045 
Justin.White@ucsf.edu 
 
Nucharee Srivirojana, PhD 
Mahidol University 
Institute for Population and Social Research 
999 Phuttamonthon 4th Road, Phutthamonthon 
Salaya, Nakhon Pathom 73170, Thailand 
Tel: +66 083-698-3588 
nucharee_s@live.com 
 
Suthat Rungruanghiranya, MD 
Srinakharinwirot University 
Faculty of Medicine 
Ongkarak, Nakhon Nayok 26120, Thailand 
Tel: +66 3739-5085 ext. 11003 
suthat109@gmail.com 

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B. Background and rationale 
 
Below, we review the evidence for several causal pathways mobilized in the proposed 
intervention. 
 
1. 
Background 
 
a. Tobacco use in low-resource settings 
 
Smoking cessation services are not widely available in low-resource settings in the developing 
world, even though 82% of the world’s 8.3 million tobacco-related deaths will occur in the 
developing world by 2030.1 Standard treatment options—nicotine replacement therapy (NRT), 
pharmacotherapy, and professional counseling—are efficacious,2, 3 but are not presently 
feasible in many places, where trained health professionals are scarce, access to health services 
is limited, and treatment is relatively expensive. Of those smokers attempting to quit, 64% do 
not use a cessation aid in the US and 90% in Thailand.4, 5 In this study, we test a novel 
intervention for promoting smoking cessation in low-resource settings. 
 
Adult male smoking prevalence exceeds 40% throughout most of Asia.6 In Thailand, daily 
smoking prevalence among men fell from 56% in 1991 to 37% in 2006, thanks in part to 
comprehensive tobacco control policies.7 Thailand’s demand for quitting remains high, such 
that half of smokers reported a quit attempt in the prior year.5 Smoking treatment programs in 
Thailand are limited to a handful of hospitals and community pharmacies, yet quit rates rose as 
high as 10% in 2007.8 Global tobacco control efforts, already underway, are expected to have 
similar effects, spurring an increased demand for quitting, throughout the developing world in 
the coming years.     
 
Thailand’s early adoption of tobacco control policies, high demand for quitting, and low use of 
professional services for smoking cessation make it an excellent setting for testing innovative 
approaches to promote quitting. Lessons from the proposed study will provide timely evidence 
for Thailand and other low-resource settings, where affordable and effective approaches are 
needed to meet a growing demand for quitting. (Outside Thailand, incentive values can be 
scaled to a similar share of income.) Moreover, a similar approach is transferrable to other 
contexts, including in rural communities, in clinics, and via private health insurers. 
 
b. Monetary incentives for health behavior change 
 
Monetary payments have been used to promote a variety of health behaviors. One systematic 
review of randomized controlled trials finds that economic incentives improved health behavior 
73% of the time.9 For example, cash incentives have successfully promoted: gym attendance,10 
adherence to medication,11 and many other behaviors. Contingency management—a substance 
abuse treatment that uses cash incentives to promote drug abstinence—raised compliance 30% 

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on average.12  These studies document the successful effects of incentives on individual health 
behaviors.   
 
 
Monetary reinforcement of health behaviors has not been uniformly successful. A systematic 
review on competitions and cash incentives for smoking cessation concludes that, although 
incentives raise short-term quit rates, these gains prove fleeting.13 Many of these prior studies 
are under-powered. The review also covers multiple interventions—lotteries, competitions, 
contingent rewards, and commitment mechanisms—making it difficult to discern the impact of 
any one design. Nonetheless, cash incentives may crowd out one’s motivation to undertake a 
health-promoting activity, or may attract smokers who are financially motivated but 
unmotivated to stay abstinent. In either case, recidivism following the reward schedule is a 
concern.  
 
 
A combination of cash incentives and commitment contracts differs from standard cash for 
quitting in two key respects. First, participants must deposit money up front, selecting for 
smokers who have a desire to be abstinent rather than those who are only motivated 
financially. We will measure the difference in program take-up across the incentives conditions 
and see if users of the incentive contracts are less likely to relapse. If so, commitment contracts 
may offer a more (cost-)effective way to target incentives. Second, the team bonus activates 
peer pressure to succeed. Very few studies address how people respond to incentives over joint 
outcomes. One exception, Babcock et al. (2011), finds that team incentives for gym attendance 
are as effective as equal-sized individual incentives, despite necessarily lowering the expected 
payoff.14 However, the study tracked a small number of students for 1 month only (2 weeks 
post-enrollment) and did not measure outcomes after payments were made.  We build on this 
promising design to test team incentives in a realistic field setting designed to have (and test) 
long-term effects in a large sample.      
 
Incentives in Workplace Wellness Programs.  Workplace wellness programs offer an important 
public health and policy opportunity to improve health, encourage prevention, and lower the 
cost of health care.  However, the success of these programs is dependent on the level of 
participation.  Voluntary participation in workplace wellness programs increases with the use of 
incentives, both financial and non-financial.15  Many programs offer monetary incentives for 
participation, compliance with behavior change recommendations, and achievement of specific 
health goals.16  The proposed study will contribute to the literature on building incentives into 
wellness programs to see if a cash bonus increases program take-up and, if so, among which 
types of employees. 
 
c. Commitment mechanisms 
 
Behavioral economists find that people exhibit a number of behaviors that are consistent with 
self-control problems. The hallmark of a self-control problem, also known as present bias, is 
that a person prefers immediate gratification to longer-term considerations.  Departure from 
long-run preferences diminishes a person’s well-being.17 Recent studies link present bias to 
health-related behaviors such as smoking and exercise.18-20  The behavioral model also suggests 

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that some individuals benefit from pre-commitments that prevent a person from indulging in 
bad behavior.21 In a U.S.-based sample, 81% of smokers used a non-binding commitment 
mechanism during a quit attempt, such as avoiding friends who smoke or places with smokers 
in order to steer clear of temptation.22 
 
 
Deposit contracts are binding, often financially-backed agreements designed to motivate a 
person to maintain self-control and achieve a specified goal. Recent literature finds that deposit 
contracts enhance an array of behaviors, such as exercise and smoking cessation,23, 24 but the 
evidence is more mixed for preventive health savings and weight loss.25, 26 Only one randomized 
controlled trial has assessed smoking cessation contracts. Giné, Karlan, and Zinman (2010) find 
that 11% of smokers in the Philippines took up the contracts.24 Average cumulative deposits 
over a 6-month period amounted to 20% of one month's income, a nontrivial commitment.  
According to the results from a surprise visit six months after the deposit period ended, the 
contracts raised the 12-month quit rate by 3.5% points (38%) from an 8.9% base.  The study has 
been influential, for example, cited by a recent NIMH panel as presenting a "novel" approach 
that might improve psychiatric treatment adherence.27  
 
 
d. Peer pressure 
 
Peer pressure has long been implicated as a cause of bad health behavior, especially among 
adolescents.  In this study, we try to activate peer pressure to foster positive behavior.  Social 
pressure is a strong regulating force for increasing willpower and motivation.28-30 Researchers 
have documented the effects of peer pressure across a range of settings: in joint liability 
microcredit groups,31 in the workplace,32, 33 and in the voting booth.34  The effects may be 
especially strong if peers know each other well.35, 36 Babcock et al. (2011) show that peer 
pressure from team incentives motivate students to exercise as much as individual incentives. 
Only three empirical studies, all randomized controlled trials, examine the use of social 
pressure as a commitment mechanism for present-biased individuals. Dupas and Robinson 
(2013) conclude that social commitment stimulated savings among present-biased members of 
a formal savings group more than a strong financial commitment.25  Kast, Meier, and Pomeranz 
(2010) find that self-help peer groups in Chile doubled savings when members had to publicly 
declare a weekly savings goal, whose attainment was publicly verified and acknowledged at a 
future meeting.37 In the design most similar to ours, Jeffery et al. (1983) assigned individuals to 
a weight loss contract in which refunded deposits depended on either individual weight loss or 
mean group weight loss.38 The group contract arm shed 5 more pounds weight than the 
individual contract arm, although group size is unreported and sample size is small.  Our study 
adds to this nascent literature by clarifying the role peer pressure can play in adhering to 
health-promoting behavior. 
 
e. Social support  
 
Social support programs have strong links to health behavior change.  Alcoholics Anonymous 
has assigned millions of new members to an experienced sponsor who provides guidance on 

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how to maintain sobriety.  Weight Watchers also assigns members to dyads. One attraction of a 
buddy system is the low marginal cost of adding the component to an existing intervention.  
Team-based interventions have been used to promote physical activity and weight loss,39, 40 
although buddy interventions, a common adjunct to smoking treatment, typically have not 
enhanced the likelihood of quitting.41 Partner interventions may raise short-term quit rates 
relative to individual therapy,42 but rarely induce long-term effects.43 Only one high-quality 
study, of which we are aware, has tested the use of financial incentives alone compared to 
incentives with group therapy. It finds that social support had an independent effect on quitting 
above and beyond the incentives.44, 45 Many other studies employ a weak research 
methodology.  By comparing depositors with and without a partner, we will re-examine the 
effect of social support in financial interventions.    
 
2. 
Rationale 
 
Tobacco use is a key contributor to premature death and morbidity in Thailand and other low- 
and middle-income countries. Within these settings, smoking cessation services are not widely 
available in many low-resource settings, because trained counselors are scarce, and 
pharmacological approaches are priced beyond the reach of many smokers. Monetary incentive 
programs for smoking cessation are a potentially scalable intervention within workplaces in 
many low-resource settings. While such programs have shown promise in high-income settings, 
they have not been tested in a middle-income country setting.  
 
We will conduct a 9-arm cluster randomized trial of large worksites located in the Bangkok 
metropolitan area of Thailand, in order to rigorously test multiple incentive designs within a 
scalable workplace setting. Our study will provide unique evidence on the effectiveness of 
adding a cash bonus and social pressure to commitment contracts. The methodology may be 
transferrable to other health behaviors and other settings. The findings will be useful for low-
resource areas where effective and cost-effective approaches are needed to meet the demand 
for quitting. The innovative scientific lessons are expected to be broadly portable, with the 
potential to influence tobacco policy across many contexts and to advance the literature on the 
use of deposit contracts and social and monetary incentives to improve health behavior. 
 
C. Study objectives 
 
The SMILE Trial (Social and Monetary Incentives for Smoking Cessation at Large Employers) was 
designed to evaluate the impact of deposit contracts, individual bonuses, and team bonuses in 
isolation and in combination, relative to each other and a no-incentive control group. 
 
The primary objective of this study is to compare the impact of multiple incentive designs 
versus usual care to increase smoking cessation among employees at participating worksites in 
the Bangkok metropolitan area of Thailand. The benchmark for effectiveness of the incentive 

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programs is usual care, offered in the form of brief group counseling and a text-messaging 
program for smoking cessation.  
 
The secondary objectives of this study are to compare the net effects across study designs, 
taking into account program take-up, heterogeneous treatment effects, cost per quitter, and 
social spillovers.  
 
 
D. Study design 
 
1. 
Study population 
 
a. Eligibility criteria for worksites 
 
Criteria for inclusion of companies in the study include:  
• At least 200 workers 
• At least 30 smokers employed at the worksite, according to estimates from worksite 
personnel   
• Willingness to implement a randomly assigned intervention and to follow all aspects of 
the study protocol  
• Being located in the Bangkok metropolitan area of Thailand 
 
These criteria will be verified during conversations with a company officer prior to inclusion of 
the company in the study. 
 
b. Eligibility criteria for participants 
 
Inclusion criteria for study participants include: 
• Being a full-time employee at a participating worksite 
• Being an adult aged 18 years old or older 
• Reporting having smoked at least 100 cigarettes in his or her lifetime 
• Reporting smoking an average of at least 10 cigarettes per week 
• Reporting wanting to quit smoking within the next 6 months 
 
All of these criteria will be verified during a screening questionnaire, to be verified during an in-
person baseline assessment.  
 
Exclusion criteria: 
• The individual expects to leave the company within the next year. 
• The individual is unable to provide informed consent.  
• The individual is currently pregnant.  

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o Pregnant women who smoke are not at higher risk from participating, but they 
belong under the supervision of a medical professional.  
 
These criteria will not be formally incorporated into a screening survey. Rather, they will be 
communicated to company officers, stated in recruitment materials and on informed consent 
form(s), and reviewed by study personnel at enrollment. 
 
2. 
Recruitment 
 
a. Recruitment of worksites 
 
We aim to recruit 100 worksites, the unit of randomization. We will target companies in or near 
several industrial areas in the Bangkok metropolitan area. Most companies in these industrial 
areas are factories that employ a large percentage of blue-collar workers. The smoking 
prevalence among blue-collar workers is believed to be higher than the general population. The 
close proximity of worksites to each other in the industrial areas will make it easier on study 
personnel to coordinate travel and logistics.  
 
The study will target large worksites located in or near six industrial areas in the Bangkok 
metropolitan area: Bang Puu, Lat Krabang, Samut Sakhon, Nawanakhon, Bang Kradee, and 
Sinsakhon. The study will also include companies in the surrounding areas of Samut Prakan, 
Pathum Thani, Lat Krabang, and Samut Sakhon, These locations cover areas to the northeast, 
southeast, and east of downtown Bangkok, The sample of worksites is expected to be broadly 
representative of industrial worksites in the Bangkok metropolitan area.  
 
We will employ a convenience sampling strategy. Even if a sample from large Bangkok 
worksites does have direct external validity to other contexts of interest, the study is still 
designed to produce results of policy significance, based on innovative testing in a design with 
strong internal validity and sufficient statistical power. A key concern will be to meet the 
sample size target of 100 units of randomization. Prior randomized trials of workplace smoking 
cessation programs have predominantly been conducted in studies within single large U.S. 
firms.  
 
Prior to recruitment, field personnel will meet with officials at the industrial agency that 
administers the industrial zone and the provincial industrial office. We will inform these 
industrial offices of our study and its aims, and invite them to serve as a formal or informal 
collaborator. Those who agree will be invited to attend a workshop of company officers and to 
act as an observer during meetings at selected worksites. We will also request a list of health 
officers or human resources personnel at the worksites within that industrial area. 
 
Recruitment of companies will follow several steps:  
1. Compile contact information for companies located in the targeted industrial areas.  

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2. During a phone conversation, give a brief introduction and request a brief in-person 
meeting to discuss the project. 
3. Send a letter with the formal request to meet to the appropriate company official as an 
email attachment. 
4. Attend an initial meeting at the worksite as an opportunity 1) to encourage the 
company officer to join the study and 2) to collect information about challenges and 
opportunities for recruitment at the company.  
5. Hold a workshop to present additional information about the study to officials from 
worksites that agree to participate in the study. 
 
b. Recruitment of participants 
 
The recruitment of participants will occur in two batches of roughly 50 worksites each. The 
second batch will begin the intervention approximately three months following the start of the 
first batch. The staggered approach is designed to relieve some of the pressure on the field 
teams of having to be active in 100 worksites at once. It will also allow for minor changes in 
logistical planning to be adopted in Batch 2. 
 
Prior to recruitment of participants, field personnel will make outreach visits to each worksite. 
During these visits, field personnel will set up a booth in a central location at the company, such 
as in the cafeteria during lunchtime, where they will provide information about the study and  
answer any questions.  
 
The recruitment of participants at each company will proceed in three phases: 
1. Identify all smokers who work at the company during a screening survey. Human 
resources and/or the health officer will assist with disseminating and collecting the 
screening surveys.  
2. Conduct a baseline survey of all smokers who are eligible for the study, as determined in 
the screening survey. 
3. Invite everyone who is eligible for the study to enroll as a participant in the study. We 
will send an invitation letter to each person, post flyers and posters around the 
worksite, and ask the health officer to assist with recruitment. 
 
3. 
Interventions 
 
The proposed study employs a cluster randomized controlled design with a 3-month 
intervention followed up 3, 6, and 12 months after enrollment.  We will randomly assign 
participating worksites to treatment arms that vary on three cross-randomized components: 1) 
deposits or no deposits, 2) bonus size (none, small, large) and 3) teammate or individual.   
 
a. Intervention components 
 
In total, there are 4 main intervention components: 

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C1. Usual care. All participants will receive usual care consisting of two elements: in-person 
group cessation counseling and cessation support via text messaging. The group counseling will 
consist of 90 minutes of counseling delivered at each worksite by a trained smoking cessation 
counselor. The text-messaging program, developed by the Thai Health Professional Alliance 
against Tobacco, will provide 1-3 messages per day for 28 days, which will include advice, 
support, and encouragement for quitting smoking. Similar programs have been found to be 
efficacious.46 All materials will be delivered in Thai. Participants who do not own a mobile 
phone will be able to designate a family member to whom the messages can be sent. If the 
person cannot identify a phone number, the person will not receive the text messages.  
 
C2. Deposits. Participants in deposit programs will be asked to provide refundable deposits 
contingent on smoking abstinence. These participants wil receive a personal deposit box to take 
home and will make an initial deposit of at least 100 baht in the deposit box at the enrollment 
meeting. The deposit boxes, made out of metal, are designed to be tamper-proof. They have a 
coin slot but no other opening. Until the follow-up assessment at 3 months, participants will be 
able to make additional deposits in a lockbox that will be kept at the company. All deposits will 
be returned at the 3-month meeting only if the person has been determined to have quit 
smoking. At the 3-month follow-up assessment, study personnel will open each box using a can 
opener and will record the total balance.  
 
At the enrollment meeting, participants will be required to give an additional 150-baht in 
collateral that depends solely on returning an intact deposit box at 3 months. The money will 
be placed in a sealed envelope with the participant’s name on it to be stored at the project 
office in a locked cabinet. If the deposit box is tampered with or not returned at 3 months, then 
the money in the sealed envelope will be forfeited to the project. 
 
C3. Teammate. Participants in team-based programs will be randomly assigned to another 
participant from the same worksite as a teammate. Team assignment will be stratified by work 
shift and native language in order to facilitate opportunities for communication. Pairings will be 
announced at the enrollment meeting at each worksite. 
 
C4. Cash bonus. Participants in small individual bonus programs will be eligible for a cash bonus 
of 600 baht for abstaining from smoking at 3 months. Participants in large individual bonus 
programs will be eligible for a bonus of 1,200 baht for abstinence at 3 months. This amount is 
roughly equivalent to one and two days’ wages, respectively. 
 
Participants in team bonus programs will be eligible for a team bonus of 1,200 baht each if both 
team members abstain from smoking at 3 months. The team bonus is designed to activate a 
sense of social commitment and peer pressure to quit. In teammate assignment strata with an 
odd number of participants, the “extra” participant did not receive a teammate and was, 
instead, eligible for a $40 individual bonus. 
  

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b. Randomization groups 
 
In total, there are 9 arms or randomization groups. The nine randomization groups are: 1) 
control group (usual care only), 2) 600-baht individual bonus, 3) 1,200-baht individual bonus, 4) 
team bonus, 5) deposits, 6) deposits plus teammate (no bonus), 7) deposits plus 600-baht 
individual bonus, 8) deposits plus 1,200-baht individual bonus, 9) deposits plus team bonus 
(Table 1).  
 
Groups 2 and 3 are similar to incentives for smoking cessation used in many studies.47 
Incorporating both allows for a test of whether larger bonuses were more effective, as some 
researchers have hypothesized.48 Group 5 is a “pure” deposit contract that replicates the 
intervention group in the CARES trial in the Philippines.24 Group 6, involving a teammate and 
deposits but no other team-based incentives, will allow for identification of the independent 
effect of buddy-based peer support. Finally, group 9 combines a deposit contract with the same 
1,200-baht team bonus in Arm 4, replicating the intervention used in White, Dow, and 
Rungruanghiranya.49 
 
 
Table 1. Crosswalk of randomization groups and intervention components 
 
 
Intervention Component 
# 
Randomization group 
Usual 
care 
Deposits 
600-
baht 
bonus 
1,200-
baht 
bonus 
Team 
1 
Control 
X 
 
 
 
 
2 
600-baht individual bonus 
X 
 
X 
 
 
3 
1,200-baht individual bonus 
X 
 
 
X 
 
4 
Team bonus 
X 
 
 
X 
X 
5 
Deposits 
X 
X 
 
 
 
6 
Deposits plus teammate 
X 
X 
 
 
X 
7 
Deposits plus 600-baht individual bonus 
X 
X 
X 
 
 
8 
Deposits plus 1,200-baht individual bonus 
X 
X 
 
X 
 
9 
Deposits plus team bonus 
X 
X 
 
X 
X 
 
 
4. 
Study procedures 
 
a. Consenting procedure 
 
The study will request consent of participants at three separate points of the study: prior to 
screening, prior to baseline assessment, and prior to enrollment in the main intervention.  
 

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The informed consent form for the screening process will be provided along with the self-
administered screening questionnaire. Consenting individuals will sign, date, and return the 
form along with their completed screening questionnaire.  
 
The informed form completed prior to the baseline assessment will occur during an in-person 
interview with study personnel. Only those individuals deemed eligible based on the screening 
questions will be asked to sign and date the baseline consent form. It covers several study 
activities, including participation in the baseline assessment and the three follow-up 
assessments (urine test, survey, and brief counseling session) to be held at 3, 6, and 12 months. 
Participation in these activities will be independent of whether the individual decides to enroll 
in the main intervention.  
 
The informed consent for enrollment in the main intervention will occur at the start of the 
enrollment meeting (discussed below). A different version of the consent form will be used for 
each arm of the intervention, corresponding to the different procedures used in each arm. 
Thus, the consent form will cover counseling at the enrollment meeting, entry into the text-
messaging program, the deposit contract, bonuses, and teammate procedures. Written consent 
will be requested from candidates after study personnel have provided a study overview and 
given an opportunity for candidates to ask questions about participation. A study personnel 
member will counter-sign and date the form.  
 
b. Screening  
 
Human resources or the health officer at each worksite will distribute a self-administered 
screening questionnaire to workplace employees. The main purpose of the screening 
questionnaire is to determine eligibility for the study. Employees will be asked to return the 
completed questionnaire form within one week. Respondents will receive an in-kind gift with a 
retail price of 35 baht (about $1). We will transfer the gifts to the company officer to distribute 
at the time that study personnel pick up the screening  questionnaire forms.  
 
c. Baseline assessment 
 
For participants who are successfully screened for eligibility and are consented into the study, 
baseline assessments are executed so that we can measure against these at Months 6 and 12 to 
calculate study outcomes.  They also ensure that the groups are balanced with respect to 
baseline characteristics. 
 
Following the baseline consent process, an interviewer will begin the baseline survey 
administered on a computer tablet. The survey will be coded into the Qualtrics offline-
compatible software application for tablets. The survey will include topics such as demographic 
characteristics, smoking characteristics, risk and time preferences, and contact information. 
 

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At the end of the baseline survey, study personnel will tell the respondent that he or she will 
receive an invitation letter to invite enrollment into the main intervention. We will provide an 
inconvenience gift worth 150 baht in cash or in kind to those who complete the baseline 
survey. In-kind gifts will consist of items such as a project t-shirt. In addition, respondents will 
receive educational brochures, stickers, and/or posters about quitting smoking.  
 
A study personnel member will contact by phone the eligible smokers who were not available 
on the day of the baseline survey. During the call, the study team member will inform the 
person that the field team will make a return visit to the company on a certain day within the 
next week, and the study team member will ask if the person is willing to take the baseline 
survey on the return visit day and, if possible, to set an appointment time. 
 
d. Enrollment  
 
After all participants from the worksite have completed the baseline survey, excluding non-
responders and attriters, we will send a personal letter to each respondent with details on the 
assigned intervention and an invitation to attend the enrollment meeting, which will take place 
about two weeks after the baseline survey. We will follow up with a phone invitation during the 
week of the enrollment meeting. In the invitation letter and during the reminder calls, we will 
emphasize the importance of arriving to the meeting on time. 
 
The enrollment meeting will take place on the premises of each participating worksite, 
scheduled in consultation with human resources or the health officer at that site. The main 
activities to occur during the enrollment meeting include:  
• Study overview tailored to each arm 
• Informed consent  
• Smoking cessation counseling  
• Developing a quit plan  
• Making an initial deposit (Arms 5-9) 
• Introduction of teammates (Arms 4, 6, 9)  
 
In order to accommodate the availability of employees, we may hold multiple meetings to take 
place at different times of day to accommodate different work schedules and work shifts. If the 
meetings occur during work hours, the coordinating officer at the company will need to inform 
supervisors at the company in an effort to get workers excused from their normal duties during 
the enrollment meeting.  
 
At the start of the enrollment meeting, a study personnel member will give a brief study 
overview and describe the specific intervention to which that company has been assigned, 
including procedures for making deposits, assignment and communication with a teammate, 
and receiving a cash bonus. At the conclusion of the study overview, attendees will be asked to 
consent to participation in the main intervention. The consent form will cover the smoking 

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cessation counseling at the enrollment meeting, the enrollee survey, and, as appropriate, the 
deposits, the bonus, and having a partner. 
 
Following the consent process, a trained smoking cessation counselor will provide group 
counseling about smoking cessation using a module developed by the Thai Health Professional 
Alliance against Tobacco.  
 
At the end of the counseling session, participants will complete a Quit Plan. This will include 
setting a specific quit date, preferably within two weeks. Participants will also be asked to start 
thinking about their first smoke-free day, how they will handle the challenges, and which types 
of activities they will substitute for smoking.  
 
Among worksites assigned to a deposit contract arm (Arms 4-7), study personnel will give each 
participant a personal deposit box. Each person will wait in line to provide to study personnel 
an initial contribution of at least 100 baht, or more if desired. Study personnel will encourage 
participants to contribute at least as much as they had typically spent on tobacco. In addition, 
participants will be asked to give the project an additional 150 baht as collateral for the safe 
return of the box, in order to deter tampering or theft. The collateral will be kept under the 
care of an appointed company representative. Each participant will sign a form to document 
that they have provided the initial contribution and collateral and will receive a deposit receipt.  
 
Among worksites assigned to a teammate arm (Arms 3, 5, 7), study personnel will announce 
pairings. If a participant’s teammate did not attend the meeting, study personnel will tell the 
person that he or she will be randomly assigned to another partner, and study personnel will 
contact the participant by phone within the next few days to inform him or her of the 
teammate’s identity. Study personnel will instruct all pairs who are present to complete a 
Teammate Support worksheet that asks teammates to share with each other their quit plan, 
including their smoking habits, how often they would like to discuss quitting with each other, 
and how they would like to encourage each other to quit smoking. 
 
At the end of the meeting, participants will receive an inconvenience gift of 150 baht in cash or 
in kind, whichever the person prefers.  
 
e. Follow-up assessments 
 
Follow-up assessments will take place at each worksite approximately 3 months, 6 months, and 
12 months after the enrollment meeting. The date will be set in consultation with human 
resources or the health officer at the worksite. All participants will be contacted by phone 
during the week of the follow-up meeting to notify them of the upcoming visit.  
 
Participants will complete two main activities during each follow-up assessment: a urine test 
and a follow-up survey. 
 

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We will use the COT One Step Cotinine Test, sold by Alfa Scientific Designs, an immunoassay 
that detects urine cotinine at a cutoff concentration of 200 ng/mL within about 10 minutes. The 
test was found to be easy to use and reliable during pre-testing.  
 
Participants will be provided with a urine specimen cup, labeled with a unique ID number as 
they enter the restroom. Study personnel will stand outside of the restroom and will collect the 
full cup as each participant exits the restroom. The cups will be brought to a nearby designated 
room where testing will take place. The assessor of the biochemical urine test will be blinded to 
participants’ randomization groups. The results of the urine test will be entered on a paper 
record and subsequently entered electronically. Following the follow-up survey described 
below, a trained smoking cessation counselor will share the urine test results with the 
participant and provide brief counseling.  
 
After providing a urine sample, each participant will complete a short survey administered by 
study personnel on a portable tablet. A separate module will be administered for self-reported 
quitters and self-reported continuing smokers, as determined at the start of the questionnaire. 
All respondents will be asked questions related to smoking behavior and quit attempts since 
the prior meeting. Participants will also be asked additional questions about their behavior 
during the intervention period and their perceptions related to the intervention. 
 
At the end of the follow-up visit, each participant will receive an inconvenience gift worth 150 
baht. Participants may choose to be paid in cash or in kind.   
 
A field team member will contact by phone the participants who do not attend the follow-up 
visit to ascertain their self-reported smoking status. The reason for non-attendance will be 
recorded. If a participant reports having abstained, a field worker will schedule a time within 
the next 48 hours to provide a urine sample for biochemical verification. Those who provide the 
urine sample will receive the inconvenience gift worth 150 baht.  
 
5. 
Randomization 
 
After baseline surveys are completed, worksites will be randomly assigned in equal proportion 
to one of the nine randomization groups. The cluster randomized design mitigated concerns of 
within-worksite contamination and is expected to be viewed by employers as more acceptable 
than person-level randomization. We will follow a covariate-adaptive procedure, in which we 
will minimize the p-value from a joint F-test as a balance criterion implemented over 1,000 
iterations.50 In Monte Carlo simulations, minimization has been found to facilitate covariate 
balance.51 The randomization procedure will include the following worksite-level covariates, 
which we will also include in the adjusted regression analyses: province, mean age, mean 
proportion born in Thailand, mean cigarettes per week, mean proportion who want to quit 
smoking within 6 months, number of employees, and estimated smoking prevalence based on 
baseline data.  
 

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A study investigator will implement the random allocation sequences using computer-
generated random numbers, concealing the sequence from field staff, company employees, 
and participants until after the baseline survey has been completed. Participants will be 
informed of their assignment in an enrollment invitation letter sent following the baseline 
survey. 
 
6. 
Outcomes  
 
The primary outcome is biochemically-verified 7-day point-prevalence smoking abstinence 
obtained 12 months after enrollment, more than 9 months after all incentives were awarded. 
To be classified as having abstained, participants will have to self-report having abstained for 
the 7 days prior to the test and to test negative for nicotine and its metabolite cotinine using a 
rapid urine test. Participants who do not complete a survey or urine test will be assumed to be 
continuing smokers as part of the intent-to-treat analysis, as is the standard practice in the 
literature.52 At each end point, we will record whether the participant indicated active use of 
nicotine replacement therapy or e-cigarettes to aid in smoking cessation. In awarding incentives 
and in analyses, users of nicotine replacement therapy or e-cigarettes who reported smoking 
abstinence were treated as abstinent.   
 
Secondary end points include biochemically verified 7-day point-prevalence abstinence at 3 
months (end of intervention) and at 6 months (3 months after the incentives end). Another 
secondary outcome will be program take-up of interventions, defined as attending the on-site 
enrollment meeting, consenting to enter the trial, and if applicable, making at least the 
minimum deposit contribution. 
 
7. 
Data management 
 
The investigators are responsible for ensuring the accuracy, completeness, legibility, and 
timeliness of the data reported. All source documents will be completed in a neat, legible 
manner to ensure accurate interpretation of data.  
 
Data collection and accurate documentation are the responsibility of the study staff under the 
supervision of the PIs. All source documents must be reviewed by the study team and data 
entry staff, who will ensure that they are accurate and complete. 
 
Survey data will be collected electronically through Qualtrics. Data on outcomes assessment 
will be recorded on paper and subsequently entered electronically.  
 
The crosswalk with personal identifiers will be transferred to the PI at the termination of 
fieldwork; the copy in Thailand will then be destroyed, and the PI will retain it for up to one 
year following the end of the study in case a scientific need arises for follow-up. Deidentified 
electronic files will be retained indefinitely. 
 

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8. 
Statistical considerations 
 
a. Sample size and statistical power 
 
The proposed sample size is 6,000 participants drawn from 100 worksites.  This sample size is 
larger than previous studies that use incentives or commitment contracts for smoking 
cessation. For example, the sample size is more than double all but one study included in a 
recent systematic review of competitions and monetary incentives for smoking cessation.13  
 
A preliminary survey of 37 firms who attended a workshop in September 2011 indicated that 
the median firm has 800 employees, roughly 20% of whom smoke. Of the 37 firms, 35 (95%) 
expressed an interest in joining the project, implying that the target of recruiting 100 worksites 
is feasible. Based on the survey data and the pilot study, we expect trial take-up to vary from 
10% of smokers in the control arm to 70% in the larger individual bonus arm, and quit rates 
conditional on take-up to vary from 20% in the control arm to 45% in the deposit contract with 
a team bonus.    
 
Using Optimal Design Software,53 we computed the minimum detectable effects for a binary 
abstinence meausre as a function of a cluster-randomized binary treatment using a multi-level 
equation (person at level 1, worksite at level 2) with a random effect for each worksite. We 
estimated that we will be able to detect absolute differences of at least 7.5 percentage points 
in abstinence rates for pairwise comparisons between any of the incentive-based arms versus 
the usual-care control group. This calculation assumed an abstinence rate of 6.0% in the control 
group (10% conditional on 60% program take-up), 60 participants per worksite, Type-I error α = 
0.05, and 80% power (β = 0.20).  
 
Our reported detectable effect sizes are conservative in that they do not adjust for stratification 
variables used for firm-level randomization (i.e., firm size, industry type, and smoking 
prevalence) or baseline control variables, both of which will reduce the variance of parameter 
estimates and, thus, the detectable effect size. 
 
b. Planned statistical analyses 
 
We will conduct descriptive analyses as components of standard data analyses. To evaluate 
balance across groups achieved by randomization, baseline values of all control variables will be 
compared across the 9 arms using t-tests. 
 
We will use generalized linear mixed-effects models to estimate the intent-to-treat effect of 
each arm and each intervention component on program take-up and smoking abstinence. The 
generalized linear mixed-effects models will include a logit link for the binary outcome and a 
random intercept at the worksite level to adjust for the clustering of participants within a 
worksite. The primary outcome variable will be verified abstinence, treating reported NRT or e-
cigarette use for cessation as abstinent as long as no cigarettes were used. We will report risk 

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differences from unadjusted and adjusted models. The adjusted models will include 
prespecified variables known to be related to the outcomes, including baseline demographic 
characteristics and smoking history. Demographic characteristics will include age (18-25, 26-35, 
36-45, ≥45), gender, household income per capita, educational attainment (0-3, 4-6, 7-12, ≥13 
years), marital status (married, not married), any children, and place of childhood (urban 
Thailand, rural Thailand, foreign country). Smoking characteristics will include average 
cigarettes per day, moderate-to-high nicotine dependence (Fagerström Test for Nicotine 
Dependence score ≥5), number of past quit attempts, number of years since initiating smoking, 
and quit intentions (want to quit within 3 months or not).   
 
In sub-analyses, we will pool Groups 2-9 to compare the average effect of receiving usual care 
plus any incentive program, compared with usual care (Group 1), using similar adjusted and 
unadjusted mixed-effects models to those described above. We will also investigate interaction 
effects between intervention components, using the same adjusted mixed-effects models as 
above. We will also investigate whether those in a bonus group or deposit group are more likely 
to relapse following the end of the incentive period.  
 
We will perform four sensitivity analyses to assess the robustness of the estimated intervention 
effects. First, we will conduct the analysis on a per-protocol basis, that is, among those who had 
accepted their assigned intervention. Second, we will use complete outcome data without 
assuming that missing cases had smoked. Third, we will exclude from the analysis the outcome 
data from participants who reported currently using NRT or e-cigarettes. Fourth, we will 
perform multiple imputation using chained equations to impute missing outcome data at each 
end point. 
 
In further statistical analyses, we will explore the relationship between time preferences 
measured at baseline and trial outcomes, as well as the peer effects that teammates have on 
each other and that participants have on non-participants who complete the baseline survey.   
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