Individual Versus Team-Based Financial Incentives to Increase Physical Activity: A Randomized, Controlled Trial

BACKGROUND

More than half of adults in the United States do not attain the minimum recommended level of physical activity to achieve health benefits. The optimal design of financial incentives to promote physical activity is unknown.

OBJECTIVE

To compare the effectiveness of individual versus team-based financial incentives to increase physical activity.

DESIGN

Randomized, controlled trial comparing three interventions to control.

PARTICIPANTS

Three hundred and four adult employees from an organization in Philadelphia formed 76 four-member teams.

INTERVENTIONS

All participants received daily feedback on performance towards achieving a daily 7000 step goal during the intervention (weeks 1- 13) and follow-up (weeks 14- 26) periods. The control arm received no other intervention. In the three financial incentive arms, drawings were held in which one team was selected as the winner every other day during the 13-week intervention. A participant on a winning team was eligible as follows: $50 if he or she met the goal (individual incentive), $50 only if all four team members met the goal (team incentive), or $20 if he or she met the goal individually and $10 more for each of three teammates that also met the goal (combined incentive).

MAIN MEASURES

Mean proportion of participant-days achieving the 7000 step goal during the intervention.

KEY RESULTS

Compared to the control group during the intervention period, the mean proportion achieving the 7000 step goal was significantly greater for the combined incentive (0.35 vs. 0.18, difference: 0.17, 95 % confidence interval [CI]: 0.07-0.28, p <0.001) but not for the individual incentive (0.25 vs 0.18, difference: 0.08, 95 % CI: -0.02-0.18, p = 0.13) or the team incentive (0.17 vs 0.18, difference: -0.003, 95 % CI: -0.11-0.10, p = 0.96). The combined incentive arm participants also achieved the goal at significantly greater rates than the team incentive (0.35 vs. 0.17, difference: 0.18, 95 % CI: 0.08-0.28, p < 0.001), but not the individual incentive (0.35 vs. 0.25, difference: 0.10, 95 % CI: -0.001-0.19, p = 0.05). Only the combined incentive had greater mean daily steps than control (difference: 1446, 95 % CI: 448-2444, p ≤ 0.005). There were no significant differences between arms during the follow-up period (weeks 14- 26).

CONCLUSIONS

Financial incentives rewarded for a combination of individual and team performance were most effective for increasing physical activity.

TRIAL REGISTRATION

Clinicaltrials.gov identifier: NCT02001194.

Statistical issues in pragmatic trials of behavioral economic interventions

BACKGROUND

Randomized clinical trials provide gold-standard evidence for the efficacy of interventions, but have limitations, including highly selected populations that make inference on effectiveness difficult and a lack of ability to adapt and change midstream.

METHODS

We propose two innovations for pragmatic trial design.

RESULTS

Evidence-based evolutionary testing, a framework that allows adaptation of interventions and rapid-cycle innovation, preserves the power of randomization while acknowledging the need for adaptation and learning. An opt-out consent framework increases the fraction of the target population who participate in trials, but may lead to dampening of effect sizes.

CONCLUSION

Pragmatic trials offer numerous advantages in the evaluation of behavioral interventions in health. Statistical innovations, including evidence-based evolutionary testing and opt-out framing of consent and enrollment processes, can enhance the power of pragmatic trials and lead to more rapid progress.

Default options in advance directives: study protocol for a randomised clinical trial

INTRODUCTION

Although most seriously ill Americans wish to avoid burdensome and aggressive care at the end of life, such care is often provided unless patients or family members specifically request otherwise. Advance directives (ADs) were created to provide opportunities to set limits on aggressive care near life's end. This study tests the hypothesis that redesigning ADs such that comfort-oriented care is provided as the default, rather than requiring patients to actively choose it, will promote better patient-centred outcomes.

METHODS AND ANALYSIS

This multicentre trial randomises seriously ill adults to receive 1 of 3 different ADs: (1) a traditional AD that requires patients to actively choose their goals of care or preferences for specific interventions (eg, feeding tube insertion) or otherwise have their care guided by their surrogates and the prevailing societal default toward aggressive care; (2) an AD that defaults to life-extending care and receipt of life-sustaining interventions, enabling patients to opt out from such care; or (3) an AD that defaults to comfort care, enabling patients to opt into life-extending care. We seek to enrol 270 patients who return complete, legally valid ADs so as to generate sufficient power to detect differences in the primary outcome of hospital-free days (days alive and not in an acute care facility). Secondary outcomes include hospital and intensive care unit admissions, costs of care, hospice usage, decision conflict and satisfaction, quality of life, concordance of preferences with care received and bereavement outcomes for surrogates of patients who die.

ETHICS AND DISSEMINATION

This study has been approved by the Institutional Review Boards at all trial centres, and is guided by a data safety and monitoring board and an ethics advisory board. Study results will be disseminated using methods that describe the results in ways that key stakeholders can best understand and implement.

TRIAL REGISTRATION NUMBER

NCT02017548; Pre-results.

Framing Financial Incentives to Increase Physical Activity Among Overweight and Obese Adults: A Randomized, Controlled Trial

BACKGROUND

Financial incentive designs to increase physical activity have not been well-examined.

OBJECTIVE

To test the effectiveness of 3 methods to frame financial incentives to increase physical activity among overweight and obese adults.

DESIGN

Randomized, controlled trial. (ClinicalTrials.gov: NCT 02030119).

SETTING

University of Pennsylvania.

PARTICIPANTS

281 adult employees (body mass index ≥27 kg/m2).

INTERVENTION

13-week intervention. Participants had a goal of 7000 steps per day and were randomly assigned to a control group with daily feedback or 1 of 3 financial incentive programs with daily feedback: a gain incentive ($1.40 given each day the goal was achieved), lottery incentive (daily eligibility [expected value approximately $1.40] if goal was achieved), or loss incentive ($42 allocated monthly upfront and $1.40 removed each day the goal was not achieved). Participants were followed for another 13 weeks with daily performance feedback but no incentives.

MEASUREMENTS

Primary outcome was the mean proportion of participant-days that the 7000-step goal was achieved during the intervention. Secondary outcomes included the mean proportion of participant-days achieving the goal during follow-up and the mean daily steps during intervention and follow-up.

RESULTS

The mean proportion of participant-days achieving the goal was 0.30 (95% CI, 0.22 to 0.37) in the control group, 0.35 (CI, 0.28 to 0.42) in the gain-incentive group, 0.36 (CI, 0.29 to 0.43) in the lottery-incentive group, and 0.45 (CI, 0.38 to 0.52) in the loss-incentive group. In adjusted analyses, only the loss-incentive group had a significantly greater mean proportion of participant-days achieving the goal than control (adjusted difference, 0.16 [CI, 0.06 to 0.26]; P = 0.001), but the adjusted difference in mean daily steps was not significant (861 [CI, 24 to 1746]; P = 0.056). During follow-up, daily steps decreased for all incentive groups and were not different from control.

LIMITATION

Single employer.

CONCLUSION

Financial incentives framed as a loss were most effective for achieving physical activity goals.

PRIMARY FUNDING SOURCE

National Institute on Aging.

Using Behavioral Economics to Design Physician Incentives That Deliver High-Value Care

Behavioral economics provides insights about the development of effective incentives for physicians to deliver high-value care. It suggests that the structure and delivery of incentives can shape behavior, as can thoughtful design of the decision-making environment. This article discusses several principles of behavioral economics, including inertia, loss aversion, choice overload, and relative social ranking. Whereas these principles have been applied to motivate personal health decisions, retirement planning, and savings behavior, they have been largely ignored in the design of physician incentive programs. Applying these principles to physician incentives can improve their effectiveness through better alignment with performance goals. Anecdotal examples of successful incentive programs that apply behavioral economics principles are provided, even as the authors recognize that its application to the design of physician incentives is largely untested, and many outstanding questions exist. Application and rigorous evaluation of infrastructure changes and incentives are needed to design payment systems that incentivize high-quality, cost-conscious care.

The Promise of Tailoring Incentives for Healthy Behaviors

PURPOSE

To describe how tailoring financial incentives for healthy behaviors to employees' goals, values, and aspirations might improve the efficacy of incentives.

DESIGN/METHODOLOGY/APPROACH

We integrate insights from self-determination theory (SDT) with principles from behavioral economics in the design of financial incentives by linking how incentives could help meet an employee's life goals, values, or aspirations.

FINDINGS

Tailored financial incentives could be more effective than standard incentives in promoting autonomous motivation necessary to initiate healthy behaviors and sustain them after incentives are removed.

RESEARCH IMPLICATIONS

Previous efforts to improve the design of financial incentives have tested different incentive designs that vary the size, schedule, timing, and target of incentives. Our strategy for tailoring incentives builds on strong evidence that difficult behavior changes are more successful when integrated with important life goals and values. We outline necessary research to examine the effectiveness of this approach among at-risk employees.

PRACTICAL IMPLICATIONS

Instead of offering simple financial rewards for engaging in healthy behaviors, existing programs could leverage incentives to promote employees' autonomous motivation for sustained health improvements.

SOCIAL IMPLICATIONS

Effective application of these concepts could lead to programs more effective at improving health, potentially at lower cost.

ORIGINALITY/VALUE

Our approach for the first time integrates key insights from SDT, behavioral economics, and tailoring to turn an extrinsic reward for behavior change into an internalized, self-sustaining motivator for long-term engagement in risk-reducing behaviors.

Comparing the effectiveness of individualistic, altruistic, and competitive incentives in motivating completion of mental exercises

This study examines the impact of individually oriented, purely altruistic, and a hybrid of competitive and cooperative monetary reward incentives on older adults' completion of cognitive exercises and cognitive function. We find that all three incentive structures approximately double the number of exercises completed during the six-week active experimental period relative to a no incentive control condition. However, the altruistic and cooperative/competitive incentives led to different patterns of participation, with significantly higher inter-partner correlations in utilization of the software, as well as greater persistence once incentives were removed. Provision of all incentives significantly improved performance on the incentivized exercises. However, results of an independent cognitive testing battery suggest no generalizable gains in cognitive function resulted from the training.

Effect of Financial Incentives to Physicians, Patients, or Both on Lipid Levels: A Randomized Clinical Trial

IMPORTANCE

Financial incentives to physicians or patients are increasingly used, but their effectiveness is not well established.

OBJECTIVE

To determine whether physician financial incentives, patient incentives, or shared physician and patient incentives are more effective than control in reducing levels of low-density lipoprotein cholesterol (LDL-C) among patients with high cardiovascular risk.

DESIGN, SETTING, AND PARTICIPANTS

Four-group, multicenter, cluster randomized clinical trial with a 12-month intervention conducted from 2011 to 2014 in 3 primary care practices in the northeastern United States. Three hundred forty eligible primary care physicians (PCPs) were enrolled from a pool of 421. Of 25,627 potentially eligible patients of those PCPs, 1503 enrolled. Patients aged 18 to 80 years were eligible if they had a 10-year Framingham Risk Score (FRS) of 20% or greater, had coronary artery disease equivalents with LDL-C levels of 120 mg/dL or greater, or had an FRS of 10% to 20% with LDL-C levels of 140 mg/dL or greater. Investigators were blinded to study group, but participants were not.

INTERVENTIONS

Primary care physicians were randomly assigned to control, physician incentives, patient incentives, or shared physician-patient incentives. Physicians in the physician incentives group were eligible to receive up to $1024 per enrolled patient meeting LDL-C goals. Patients in the patient incentives group were eligible for the same amount, distributed through daily lotteries tied to medication adherence. Physicians and patients in the shared incentives group shared these incentives. Physicians and patients in the control group received no incentives tied to outcomes, but all patient participants received up to $355 each for trial participation.

MAIN OUTCOMES AND MEASURES

Change in LDL-C level at 12 months.

RESULTS

Patients in the shared physician-patient incentives group achieved a mean reduction in LDL-C of 33.6 mg/dL (95% CI, 30.1-37.1; baseline, 160.1 mg/dL; 12 months, 126.4 mg/dL); those in physician incentives achieved a mean reduction of 27.9 mg/dL (95% CI, 24.9-31.0; baseline, 159.9 mg/dL; 12 months, 132.0 mg/dL); those in patient incentives achieved a mean reduction of 25.1 mg/dL (95% CI, 21.6-28.5; baseline, 160.6 mg/dL; 12 months, 135.5 mg/dL); and those in the control group achieved a mean reduction of 25.1 mg/dL (95% CI, 21.7-28.5; baseline, 161.5 mg/dL; 12 months, 136.4 mg/dL; P < .001 for comparison of all 4 groups). Only patients in the shared physician-patient incentives group achieved reductions in LDL-C levels statistically different from those in the control group (8.5 mg/dL; 95% CI, 3.8-13.3; P = .002).

CONCLUSIONS AND RELEVANCE

In primary care practices, shared financial incentives for physicians and patients, but not incentives to physicians or patients alone, resulted in a statistically significant difference in reduction of LDL-C levels at 12 months. This reduction was modest, however, and further information is needed to understand whether this approach represents good value.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT01346189.

Web-Based Access to Positive Airway Pressure Usage with or without an Initial Financial Incentive Improves Treatment Use in Patients with Obstructive Sleep Apnea

STUDY OBJECTIVES

We tested whether providing adults with obstructive sleep apnea (OSA) with daily Web-based access to their positive airway pressure (PAP) usage over 3 mo with or without a financial incentive in the first week improves adherence and functional outcomes.

SETTING

Academic- and community-based sleep centers.

PARTICIPANTS

One hundred thirty-eight adults with newly diagnosed OSA starting PAP treatment.

INTERVENTIONS

Participants were randomized to: usual care, usual care with access to PAP usage, or usual care with access to PAP usage and a financial incentive. PAP data were transmitted daily by wireless modem from the participants' PAP unit to a website where hours of usage were displayed. Participants in the financial incentive group could earn up to $30/day in the first week for objective PAP use ≥ 4 h/day.

MEASUREMENTS AND RESULTS

Mean hours of daily PAP use in the two groups with access to PAP usage data did not differ from each other but was significantly greater than that in the usual care group in the first week and over 3 mo (P < 0.0001). Average daily use (mean ± standard deviation) during the first week of PAP intervention was 4.7 ± 3.3 h in the usual care group, and 5.9 ± 2.5 h and 6.3 ± 2.5 h in the Web access groups with and without financial incentive respectively. Adherence over the 3-mo intervention decreased at a relatively constant rate in all three groups. Functional Outcomes of Sleep Questionnaire change scores at 3 mo improved within each group (P < 0.0001) but change scores of the two groups with Web access to PAP data were not different than those in the control group (P > 0.124).

CONCLUSIONS

Positive airway pressure adherence is significantly improved by giving patients Web access to information about their use of the treatment. Inclusion of a financial incentive in the first week had no additive effect in improving adherence.

A randomized controlled trial of co-payment elimination: the CHORD trial

OBJECTIVES

Efforts to improve adherence by reducing co-payments through value-based insurance design are become more prevalent despite limited evidence of improved health outcomes. The objective of this study was to determine whether eliminating patient co-payments for blood pressure medications improves blood pressure control.

STUDY DESIGN

Randomized controlled trial.

METHODS

The Collaboration to Reduce Disparities in Hypertension (CHORD) was a randomized controlled trial with 12 months' follow-up conducted among patients from the Philadelphia and Pittsburgh Veterans Administration Medical Centers. We enrolled 479 patients with poorly controlled systolic blood pressure. Participants were randomly assigned to: a) receive reductions in co-payments from $8 to $0 per medication per month for each antihypertensive prescription filled, b) a computerized behavioral intervention (CBI), c) both co-pay reduction and CBI, or d) usual care. Our main outcome measure was change in systolic blood pressure from enrollment to 12 months post enrollment. We also measured adherence using the medication possession ratio in a subset of participants.

RESULTS

There were no significant interactions between the co-payment interventions and the CBI interventions. There was no relative difference in the change in medication possession ratio between baseline and 12 months (0.05% and -.90% in control and incentive groups, respectively; P = .74) or in continuous medication gaps of 30, 60, or 90 days. Blood pressure decreased among all participants, but to a similar degree between the financial incentive and control groups. Systolic pressure within the incentive group dropped 13.2 mm Hg versus 15.2 mm Hg for the control group (difference = 2.0; 95% CI, -2.3 to 6.3; P = .36). The proportion of patients with blood pressure under control at 12 months was 29.5% in the incentive group versus 33.9 in the control group (odds ratio, 0.8; 95% CI, 0.5-1.3; P = .36).

CONCLUSIONS

Among patients with poorly controlled blood pressure, financial incentives--as implemented in this trial--that reduced patient cost sharing for blood pressure medications did not improve medication adherence or blood pressure control.

Effects of a Medical Home and Shared Savings Intervention on Quality and Utilization of Care

IMPORTANCE

Published evaluations of medical home interventions have found limited effects on quality and utilization of care.

OBJECTIVE

To measure associations between participation in the Northeastern Pennsylvania Chronic Care Initiative and changes in quality and utilization of care.

DESIGN, SETTING, AND PARTICIPANTS

The northeast region of the Pennsylvania Chronic Care Initiative began in October 2009, included 2 commercial health plans and 27 volunteering small primary care practice sites, and was designed to run for 36 months. Both participating health plans provided medical claims and enrollment data spanning October 1, 2007, to September 30, 2012 (2 years prior to and 3 years after the pilot inception date). We analyzed medical claims for 17,363 patients attributed to 27 pilot and 29 comparison practices, using difference-in-difference methods to estimate changes in quality and utilization of care associated with pilot participation.

EXPOSURES

The intervention included learning collaboratives, disease registries, practice coaching, payments to support care manager salaries and practice transformation, and shared savings incentives (bonuses of up to 50% of any savings generated, contingent on meeting quality targets). As a condition of participation, pilot practices were required to attain recognition by the National Committee for Quality Assurance as medical homes.

MAIN OUTCOMES AND MEASURES

Performance on 6 quality measures for diabetes and preventive care; utilization of hospital, emergency department, and ambulatory care.

RESULTS

All pilot practices received recognition as medical homes during the intervention. By intervention year 3, relative to comparison practices, pilot practices had statistically significantly better performance on 4 process measures of diabetes care and breast cancer screening; lower rates of all-cause hospitalization (8.5 vs 10.2 per 1000 patients per month; difference, -1.7 [95% CI, -3.2 to -0.03]), lower rates of all-cause emergency department visits (29.5 vs 34.2 per 1000 patients per month; difference, -4.7 [95% CI, -8.7 to -0.9]), lower rates of ambulatory care-sensitive emergency department visits (16.2 vs 19.4 per 1000 patients per month; difference, -3.2 [95% CI, -5.7 to -0.9]), lower rates of ambulatory visits to specialists (104.9 vs 122.2 per 1000 patients per month; difference, -17.3 [95% CI, -26.6 to -8.0]); and higher rates of ambulatory primary care visits (349.0 vs 271.5 per 1000 patients per month; difference, 77.5 [95% CI, 37.3 to 120.5]).

CONCLUSIONS AND RELEVANCE

During a 3-year period, this medical home intervention, which included shared savings for participating practices, was associated with relative improvements in quality, increased primary care utilization, and lower use of emergency department, hospital, and specialty care. With further experimentation and evaluation, such interventions may continue to become more effective.

A randomized controlled trial of negative co-payments: the CHORD trial

OBJECTIVES

Value-based insurance designs are being widely used. We undertook this study to examine whether a financial incentive that lowered co-payments for blood pressure medications below $0 improved blood pressure control among patients with poorly controlled hypertension.

STUDY DESIGN

Randomized controlled trial.

METHODS

Participants from 3 Pennsylvania hospitals (n = 337) were randomly assigned to: a) be paid $8 per medication per month for filling blood pressure prescriptions, b) a computerized behavioral intervention (CBI), c) both payment and CBI, or d) usual care. The primary outcome was change in blood pressure between baseline and 12 months post enrollment. We also measured adherence using the medication possession ratio in a subset of participants.

RESULTS

There were no significant interactions between the incentive and the CBI interventions. There were no significant changes in medication possession ratio in the treatment group. Blood pressure decreased among all participants, but to a similar degree between the financial incentive and control groups. Systolic blood pressure (SBP) dropped 13.7 mm Hg for the incentive group versus 10.0 mm Hg for the control group (difference = –3.7; 95% CI, –9.0 to 1.6; P = .17). The proportion of patients with blood pressure under control 12 months post enrollment was 35.6% of the incentive group versus 27.7% of the control group (odds ratio, 1.4; 95% CI, 0.8-2.5; P = .19). Diabetics in the incentive group had an average drop in SBP of 12.7 mm Hg between baseline and 12 months compared with 4.0 mm Hg in the control group (P = .02). Patients in the incentive group without diabetes experienced average SBP reductions of 15.0 mm Hg, compared with 16.3 mm Hg for control group nondiabetics (P = .71).

CONCLUSIONS

Among patients with poorly controlled blood pressure, financial incentives—as implemented in this trial—did not improve blood pressure control or adherence except among patients with diabetes.

ACA-mandated elimination of cost sharing for preventive screening has had limited early impact

OBJECTIVES

The Affordable Care Act eliminated patient cost sharing for evidence-based preventive care, yet the impact of this policy on colonoscopy and mammography rates is unclear. We examined the elimination of cost sharing among small business beneficiaries of Humana, a large national insurer.

STUDY DESIGN

This was a retrospective interrupted time series analysis of whether the change in cost-sharing policy was associated with a change in screening utilization, using grandfathered plans as a comparison group.

METHODS

We compared beneficiaries in small business nongrandfathered plans that were required to eliminate cost sharing (intervention) with those in grandfathered plans that did not have to change cost sharing (control). There were 63,246 men and women aged 50 to 64 years eligible for colorectal cancer screening, and 30,802 women aged 50 to 64 years eligible for breast cancer screening. The primary outcome variables were rates of colonoscopy and mammography per person-month, with secondary analysis of colonoscopy rates coded as preventive only.

RESULTS

There was no significant change in the level or slope of colonoscopy and mammography utilization for intervention plans relative to the control plans. There was also no significant relevant change among those colonoscopies coded as preventive.

CONCLUSIONS

The results suggest that the implementation of the policy is not having its intended effects, as cost sharing rates for colonoscopy and mammography did not change substantially, and utilization of colonoscopy and mammography changed little, following this new policy approach.

Randomized trial of four financial-incentive programs for smoking cessation

BACKGROUND

Financial incentives promote many health behaviors, but effective ways to deliver health incentives remain uncertain.

METHODS

We randomly assigned CVS Caremark employees and their relatives and friends to one of four incentive programs or to usual care for smoking cessation. Two of the incentive programs targeted individuals, and two targeted groups of six participants. One of the individual-oriented programs and one of the group-oriented programs entailed rewards of approximately $800 for smoking cessation; the others entailed refundable deposits of $150 plus $650 in reward payments for successful participants. Usual care included informational resources and free smoking-cessation aids.

RESULTS

Overall, 2538 participants were enrolled. Of those assigned to reward-based programs, 90.0% accepted the assignment, as compared with 13.7% of those assigned to deposit-based programs (P<0.001). In intention-to-treat analyses, rates of sustained abstinence from smoking through 6 months were higher with each of the four incentive programs (range, 9.4 to 16.0%) than with usual care (6.0%) (P<0.05 for all comparisons); the superiority of reward-based programs was sustained through 12 months. Group-oriented and individual-oriented programs were associated with similar 6-month abstinence rates (13.7% and 12.1%, respectively; P=0.29). Reward-based programs were associated with higher abstinence rates than deposit-based programs (15.7% vs. 10.2%, P<0.001). However, in instrumental-variable analyses that accounted for differential acceptance, the rate of abstinence at 6 months was 13.2 percentage points (95% confidence interval, 3.1 to 22.8) higher in the deposit-based programs than in the reward-based programs among the estimated 13.7% of the participants who would accept participation in either type of program.

CONCLUSIONS

Reward-based programs were much more commonly accepted than deposit-based programs, leading to higher rates of sustained abstinence from smoking. Group-oriented incentive programs were no more effective than individual-oriented programs. (Funded by the National Institutes of Health and CVS Caremark; ClinicalTrials.gov number, NCT01526265.).

The Role of Behavioral Economic Incentive Design and Demographic Characteristics in Financial Incentive-Based Approaches to Changing Health Behaviors: A Meta-Analysis

Objective.

To evaluate the use of behavioral economics to design financial incentives to promote health behavior change and to explore associations with demographic characteristics.

Data Source.

Studies performed by the Center for Health Incentives and Behavioral Economics at the University of Pennsylvania published between January 2006 and March 2014.

Study Inclusion and Exclusion Criteria.

Randomized, controlled trials with available participant-level data. Studies that did not use financial incentives to promote health behavior change were excluded.

Data Extraction.

Participant-level data from seven studies were pooled.

Data Synthesis.

Meta-analysis on the pooled sample using a random-effects model with interaction terms to examine treatment effects and whether they varied by incentive structure or demographic characteristics.

Results.

The pooled study sample comprised 1403 participants, of whom 35% were female, 70% were white, 24% were black, and the mean age was 48 years (standard deviation 11.2 years). In the fully adjusted model, participants offered financial incentives had higher odds of behavior change (odds ratio [OR]: 3.96; p < .01) when compared to control. There were no significant interactions between financial incentives and gender, age, race, income, or education. When further adjusting for incentive structure, blacks had higher odds than whites of achieving behavior change (OR: 1.67; p< .05) with a conditional payment. Compared to lower-income participants, higher-income participants had lower odds of behavior change (OR: 0.46; p = .01) with a regret lottery.

Conclusion.

Financial incentives designed using concepts from behavioral economics were effective for promoting health behavior change. There were no large and consistent relationships between the effectiveness of financial incentives and observable demographic characteristics. Second-order examinations of incentive structure suggest potential relationships among the effectiveness of financial incentives, incentive structure, and the demographic characteristics of race and income.

Preference-adaptive randomization in comparative effectiveness studies

BACKGROUND

Determination of comparative effectiveness in a randomized controlled trial requires consideration of an intervention's comparative uptake (or acceptance) among randomized participants and the intervention's comparative efficacy among participants who use their assigned intervention. If acceptance differs across interventions, then simple randomization of participants can result in post-randomization losses that introduce bias and limit statistical power.

METHODS

We develop a novel preference-adaptive randomization procedure in which the allocation probabilities are updated based on the inverse of the relative acceptance rates among randomized participants in each arm. In simulation studies, we determine the optimal frequency with which to update the allocation probabilities based on the number of participants randomized. We illustrate the development and application of preference-adaptive randomization using a randomized controlled trial comparing the effectiveness of different financial incentive structures on prolonged smoking cessation.

RESULTS

Simulation studies indicated that preference-adaptive randomization performed best with frequent updating, accommodated differences in acceptance across arms, and performed well even if the initial values for the allocation probabilities were not equal to their true values. Updating the allocation probabilities after randomizing each participant minimized imbalances in the number of accepting participants across arms over time. In the smoking cessation trial, unexpectedly large differences in acceptance among arms required us to limit the allocation of participants to less acceptable interventions. Nonetheless, the procedure achieved equal numbers of accepting participants in the more acceptable arms, and balanced the characteristics of participants across assigned interventions.

CONCLUSIONS

Preference-adaptive randomization, coupled with analysis methods based on instrumental variables, can enhance the validity and generalizability of comparative effectiveness studies. In particular, preference-adaptive randomization augments statistical power by maintaining balanced sample sizes in efficacy analyses, while retaining the ability of randomization to balance covariates across arms in effectiveness analyses.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT01526265; 31 January 2012.