Effect of Lottery Incentives on Study Protocol Adherence in the AZ-HEROES Study - A Retrospective Cohort Study

Background: Various monetary incentive strategies have been used to increase participant adherence in research. Our study examined the impact of two lottery incentive amounts on study adherence.Aims/objectives: The objective of this paper was to quantify the impact of a $50 and $100 lottery incentive on adherence to weekly study activities among AZ HEROES participants.Methods: The AZ HEROES study was a prospective cohort study examining COVID-19 infections among Arizona frontline workers. Participants submitted weekly nasal swabs to detect COVID-19 infections and completed surveys. To increase adherence, a $50 lottery was implemented with random winners selected each week among those fully adherent over 4 weeks, and later increased to $100. Mixed effects logistic regression modelled the association between lottery implementation and adherence.Results: After adjusting for enrollment date, baseline adherence, sex, age, household income, COVID-19 result, and occupation, the odds of adherence after the $50 lottery implementation were 1.53 (95% CI: 1.29, 1.83) and after the $100 lottery implementation were 1.79 (95% CI: 1.48, 2.17) times the odds before the lottery.Conclusion: After adjustment, adherence increased post implementation of the $50 and $100 lotteries. These findings suggest that a lottery incentive may increase participant adherence, and further research is warranted.