The Effectiveness and Ethics of Incentives for Research Participation: Two Embedded Randomized Recruitment Trials

Abstract

Background: Using financial incentives to improve research participation is controversial and variably regulated due to uncertainty regarding whether incentives serve as undue inducements by blunting peoples’ sensitivity to research risks, or unjust inducements by preferentially increasing enrollment among disadvantaged persons. Methods: Patients were randomly assigned to incentives of $0, $200, or $500 for participating in a trial comparing smoking cessation interventions, and to $0, $100, or $300 for participating in a trial evaluating an ambulation intervention. Each incentive trial was powered to rule out interactions between incentive size and perceived research risk (undue inducement), and between incentive size and income (unjust inducement), on the primary outcome of consenting to the parent trial. Findings: Incentives significantly increased enrollment among 654 patients in the smoking cessation trial (adjusted odds ratio (OR) for each increase in incentive = 1.70, 95% confidence interval (CI) = 1.34 – 2.17; p < 0.001), but not among 642 patients in the ambulation trial (adjusted OR = 0.88, 95% CI = 0.64 – 1.22; p = 0.45). In both trials, undue and unjust inducement were ruled out (upper confidence limits of ORs for undue inducement = 1.15 and 0.99, both p < 0.001; upper confidence limits of ORs for unjust inducement = 1.21 and 1.26, p = 0.011 and p < 0.001, respectively). In both trials, larger incentives were associated with more time spent reviewing consent forms (both p < 0.005). Incentives were not associated with perceived research risks, trial understanding, perceptions of coercion, or therapeutic misconceptions in either trial. Interpretation: Financial incentives increased trial enrollment in one of two trials, and did not produce undue or unjust inducement or other unintended consequences in either trial. Trial Registration: ClinicalTrials.gov number, NCT02697799. Funding Statement: National Cancer Institute. Declaration of Interests: We declare no competing interests. Ethics Approval Statement: Approved by IRBs at the University of Pennsylvania and Northwestern University, using a waiver of the requirement for informed consent. The trials were also guided by an Ethics Advisory Board and overseen by a Data and Safety Monitoring Board (DSMB).