In two small-scale studies, we demonstrate that a lottery-based financial incentive coupled with a simple reminder system substantially improved the rate of non-adherence to warfarin compared with historic controls, accompanied by a large improvement in anticoagulation control relative to their baseline values at a state-of-the-art anticoagulation clinic, While there is controversy about whether such payments to patients should be used [25
], the degree of improvement observed in non-adherence rates in this pilot is striking.
The fact that subjects' proportion of INRs out of range returned to close to their baseline values post-intervention indicates that while the lottery-based incentive appeared to be effective in improving anticoagulation control, longer-term administration of the incentive program is likely necessary. It would be important to know whether a sustained effect can be attained through longer-term administration of the intervention; for example, would people internalize improved medication taking habits if the intervention were longer-standing? It is also possible that longer-range administration of the adherence-improving intervention may be necessary to sustained improved adherence. Longer-term administration of this intervention could be cost effective for high-risk patients on warfarin given the high risk of stroke and other thrombotic complications.
Lotteries used as incentives have had some success in altering health behaviors [27
]. Small payouts, e.g., $10 to quit smoking, may not be effective [28
], but knowledge about the effectiveness of lotteries in this regard is limited, as nearly all lottery-based studies to date have used rewards with low expected values and did not provide daily payouts. In the only study to have previously used daily lotteries, our group found that a lottery similar in design to the lottery used in this study with an expected value of $3 per day led to significant amounts of weight loss relative to a control group[29
] Lotteries with larger expected values and daily lotteries, to our knowledge, have never been tested in the context of medication adherence.
The lottery incentive was designed to take advantage of several effects identified in the behavioral economics literature on incentives. First, consistent with research showing that even small rewards and punishments can have great incentive value if they occur immediately [21
], adherent patients received rapid feedback about whether they won and non-adherent subjects received feedback about whether they would have won had they been adherent. Second, based on research showing that people are motivated by the experience of past rewards and the prospect of future rewards [32
] and that people are particularly emotionally attracted to small probabilities of large rewards [33
], the lottery was tailored to provide frequent small payoffs (a 1 or 2 in 5 chance at a $10 reward) and infrequent large payoffs (a 1 in 100 chance at a $100 reward). Third, research on decision making has found that the desire to avoid regret is a potent force in decision making under risk [23
]. By giving non-adherent patients feedback about what they would have won had they been adherent, the incentive scheme was designed to maximize the threat of regret if people failed to adhere. Lotteries may be more effective than fixed payments (e.g. $3 per day), as people tend to overweigh small probabilities in making decisions [23
] and playing a daily lottery may have entertainment value that offsets some of the tedium of taking daily medications.
The major limitation of this study is that it was not conducted as a randomized controlled trial. However, the within-subject improvement in INRs as well as the improvements in adherence both among subjects in whom we had MEMS cap adherence data pre-intervention and compared to historical controls were quite large. Nonetheless, demonstration of the effectiveness of this intervention will ultimately require a randomized trial ideally with longer-term follow-up to examine the sustainability of this approach. Examination of cost effectiveness will also be important to determine the likelihood of adoption by payers.
The success of the intervention raises ethical issues. First, there could be an objection to paying people to 'do things that they should do anyway.' However, the behavioral economics literature finds that even highly motivated individuals often have difficulty in making decisions in the short term that favor their long-term interests [36
]. A lottery (or other reward system that provides frequent positive reinforcement) can be thought of as a way to help patients to internalize these long-term benefits so they make decisions in the short-term that favor their long-term interests. From the standpoint of a payor, a similar amount of money could be used to treat strokes that result from non-use of warfarin, or to provide an incentive system like this, which reduces the rate of strokes, which is clearly a better outcome for the patients. Second there could be a concern that rewarding patients to take medication could reduce their sense of personal responsibility for their health and hence adherence if and when incentives are removed. However, our study provided no evidence of such a negative rebound effect, and it may be true that any long-term changes in behavior induced by incentives would persist due to the establishment of adherent habits.