Conflicts of Interest Among Patient and Consumer Representatives to U.S. Food and Drug Administration Drug Advisory Committees

IN RESPONSE: Drs. Weinstock and Petry note that behavior change is complex and reinforcement is an important component of interventions to increase physical activity. Although we agree with these comments, our study focused on the effect of different ways to frame financial incentives. Our findings show that, holding reinforcement constant, financial incentives framed as a loss were most effective. A prior study by Drs. Weinstock and Petry revealed important insights but should be compared with our study with caution, because theirs was smaller, did not target overweight and obese adults, used a different step goal, and had a different primary outcome measure (1). Drs. Mitchell and Oh question the appropriateness of the same 7000-step goal for different participants. We agree that persons may vary in their baseline activity level; however, we noted as a limitation that baseline data were not available. We also provided several reasons supporting a 7000-step goal, including its endorsement by the American College of Sports Medicine (2). Many prior studies have used a 10000-step goal; however, this target has been shown to disengage more sedentary persons who could benefit the most from these types of interventions (3). Drs. Mitchell and Oh also state that tracking step counts will vary on the basis of how a device is carried. We agree, but this statement is true for any device, not just smartphones. In addition, our prior work found that smartphones varied less in tracking step counts than wearable devices (4). Drs. Mitchell and Oh also comment that the control group may have increased their activity because of the participation incentive. Although this could be true, the same participation incentive was used for all study groups; therefore, we were able to evaluate the differential effect of the intervention incentives, which was our primary goal. We agree that more research is needed to evaluate how to sustain behavior change for longer periods. These comments highlight that behavior change is hard and driven by many factors. However, our findings show that insights from behavioral economics can improve the effectiveness of financial incentivebased interventions for physical activity.