Incentive programmes for smoking cessation: cluster randomized trial in workplaces in Thailand.

Objective: To compare several monetary incentive programmes for promoting smoking abstinence among employees who smoke at workplaces in a middle income country.

Design: Parallel group, open label, assessor blinded, cluster randomized controlled trial.

Setting: Large industrial workplaces in metropolitan Bangkok, Thailand.

Participants: Employees who smoked cigarettes and planned to quit within six months recruited from 101 worksite clusters (84 different companies).

Interventions: Worksites were digitally cluster randomized by an independent investigator to usual care or usual care plus one of eight types of incentive programmes. Usual care consisted of one time group counseling and cessation support through a 28 day text messaging programme. The incentive programmes depended on abstinence at three months and varied on three intervention components: refundable deposits, assignment to a teammate, and bonus size ($20 (£15; €17) or $40).

Main Outcome Measures: The primary outcome was biochemically verified seven day point prevalence smoking abstinence at 12 months. Secondary outcomes were programme acceptance at enrollment and smoking abstinence at three months (end of intervention) and at six months. All randomized participants who had complete baseline information were included in intention-to-treat analyses; participants with missing outcomes were coded as continuing smokers.

Results: Between April 2015 and August 2016, the trial enrolled 4190 participants. Eighteen were omitted because of missing baseline covariates and death before the primary endpoint, therefore 4172 participants were included in the intention-to-treat analyses. Programme acceptance was relatively high across all groups: 58.7% (2451/4172) overall and 61.3% (271/442) in the usual care group. Abstinence rates at 12 months did not differ among deposit programmes (336/2253, 14.9%) and non-deposit programmes (280/1919, 14.6%; adjusted difference 0.8 points, 95% confidence interval -2.7 to 4.3, P=0.65), but were somewhat lower for team based programmes (176/1348, 13.1%) than individual based programmes (440/2824, 15.6%; -3.2 points, -6.6 to -0.2, P=0.07), and higher for $40 bonus programmes (322/1954, 16.5%) than programmes with no bonus (148/1198, 12.4%; 5.9 points, 2.1 to 9.7, P=0.002). The $40 individual bonus was the most efficacious randomization group at all endpoints. Intervention components did not strongly interact with each other.

Conclusions: Acceptance of monetary incentive programmes for promoting smoking abstinence was high across all groups. The $40 individual bonus programmes increased long term smoking abstinence compared with usual care, although several other incentive designs did not, such as team based programmes and deposit programmes. Incentive design in workplace wellness programmes might influence their effectiveness at reducing smoking rates in low resource settings.

Trial Registration: ClinicalTrials.gov (NCT02421224).