Higher incentive amounts do not appear to be associated with greater quit rates in financial incentive programmes for smoking cessation

Introduction: Financial incentive (FI) programmes can promote smoking cessation. While foundational research suggests higher FI amounts may better produce outcomes, confirmation is needed. Further, the optimal amount(s) needed to cost-effectively promote change is unclear. Our objective was to reconfirm whether higher amounts are associated with greater quitting through review of previous programmes, before assessing whether non-linear trends and obvious inflections in this relationship exist which may highlight optimal amounts.

Methods: Four databases were searched for controlled or randomised controlled studies which detailed FI programmes for smoking cessation in adults.

Results: Twenty-six studies were included. Programmes varied in length (3.0-52.0 weeks, median = 12.0), FI provision timing, and longest follow-up (5.5-24.0 months, median = 6.0). The odds ratio of quitting at longest follow-up ranged from 0.32 to 5.89. Maximum FI amounts were between US$106.19 and $4,027.92. Quit rates and amounts were not significantly correlated. Subsequent comparisons to reduce between-study variations were non-significant. Further analyses revealed no evidence of non-linear fits, changes in inflection, or cut-points.

Conclusions: While higher FI amounts were not associated with greater quitting within this review, the limited data available and variations in target populations and programme designs unrelated to the amount have undoubtedly influenced results. Findings suggest information on this relationship and optimal FI amounts are not determinable through current evidence. As this information is important for cost-effectiveness evaluations and real-world viability, further investigation is necessary. Laboratory research could provide valuable initial insight. Trials comparing programme efficacy under the identified amounts could then be implemented.