Mina Kwon - 2019.10.15 -
Randomized Clinical Trial ?
Randomized Clinical Trial • Purpose: assess treatment’s efficacy or effectiveness • “randomized”: random assignment to each study group — implies balance in baseline characteristics between groups —allows eliminating many pre-analytical differences that might bias the entire study https://www.statisticshowto.datasciencecentral.com/experimental-design/randomized-clinical-trial-rcts/
Randomized Clinical Trial Francesco et al (2017) • Select intervention that could be correctly assessed • Choose and report randomization methods correctly • Balance groups using stratification technique • Blinding • Intention to treat analysis (ITT) Francesco, Stephane, Fabrizio, Pier (2017) How to design a randomized clinical trial: tips and tricks for conduct a successful study in thoracic disease domain, Journal of Thoracic Disease;9(8)
Randomized Clinical Trial https://www.statisticshowto.datasciencecentral.com/experimental-design/randomized-clinical-trial-rcts/
Introduction
Introduction • Physical inactivity, a major risk factor for disability and death • Challenge in motivating individuals to increase physical activity • Financial rewards, a useful tool for encouraging healthy behavior!
Introduction • “Financial incentives for physical activity in adults: systematic review and meta-analysis” (Mitchell, Orstad, Biswas et al; 2019) Key principles of effective incentive design to promote physical activity 1) immediate incentives 2) realistic daily goals 3) longer interventions (>24 weeks) 4) frequent and personalized feedback + Size of incentives does not have to be large
Introduction • HOWEVER, much still remains unknown 1. HOW to distribute the small incentives over time, for maximal effect? 2. HOW to create behavior change that is sustained after incentives are inevitably removed?
Introduction Simple CONSTANT incentive Prevent tolerance INCREASING incentive Diminish reliance on financial reward DECREASING incentive & Motivate initiation
Primary objective Comparing 3 different CONSTANT INCREASING DECREASING 2-week incentive programs with rewards for daily steps taken to determine which was the most effective for increasing the number of steps both during and after the intervention
METHOD
Study Design • Experiment with online platform (“Achievement”) recording daily steps of users through pedometers
Study Design • Experiment with online platform (“Achievement”) recording daily steps of users through pedometers • Intervention: offering 20-fold incentives for 2 weeks. • Pre-intervention Intervention Follow-up 3 weeks 2 weeks 3 weeks
Study Design 10,000 steps = $0.01 CONTROL CONSTANT 10,000 steps = $2 INCREASING DECREASING 10,000 steps = $0.05 $3.5 10,000 steps = $ 3.5 $0.05
Participants CONTROL CONSTANT INCREASING DECREASING
Statistical Analysis 1. Test the effect of 20-fold incentive increase on walking behavior VS CONTROL CONSTANT INCREASING DECREASING 2. Test the effect of incentive structure VS VS CONSTANT INCREASING DECREASING
Statistical Analysis • Handling Missing data Missing data: any day with fewer than 2000 recorded steps. 1) Intent-to-treat strategy (ITT) : replace missing data with a mean of a given participant’s preintervention daily step counts greater than 2000 steps. 2) Sensitivity Analysis : deleted all daily step data recording fewer than 2000 steps.
Statistical Analysis • Ordinary least squares regression to determine the overall and separate effects of 3 treatment groups on participants daily steps. • Wald test to assess differences between treatment conditions • Cost-effectiveness analysis of additional steps taken per $1 paid to each treatment condition participant relative to control participant
Statistical Analysis • Ordinary least squares regression to determine the overall and separate effects of 3 treatment groups on participants daily steps. • Wald test to assess differences between treatment conditions • Cost-effectiveness analysis of additional steps taken per $1 paid to each treatment condition participant relative to control participant
RESULTS
1. E ff ect of 20-fold increase in incentive • Intervention period > CONSTANT INCREASING CONTROL DECREASING 135.0 additional daily steps (95% CI, 41.0 - 228.9 steps) • Postintervention period: No significant difference
2. E ff ect of Incentive Structure • During the Intervention 306.7 additional daily steps 96.9 additional daily steps > (95% CI, 91.5 - 521.9 steps) CONTROL DECREASING CONTROL (95% CI, 15.3 - 178.5 steps) p = .005 p = .02 > 305.1 additional daily steps > 95.3 additional daily steps INCREASING DECREASING INCREASING (95% CI, 89 - 512.2 steps) (95% CI, 11.3 - 179.3 steps) CONSTANT p = .006 p = .03 ~ ~ 209.8 additional daily steps 1.5 additional daily steps DECREASING INCREASING CONTROL (95% CI, -5.7 - 425.3 steps) (95% CI, -81.6 - 84.7 steps) p = .06 p = .97 7300 7200 7100 7000 6900 constant increasing decreasing control d P < .01. e P <.05. f P <.10.
2. E ff ect of Incentive Structure • After the Intervention Week 1 Week 2 Week 3 CONTROL 329.5 additional daily steps (95% CI, 20.6 - 638.4 steps) p = .04 > > > INCREASING CONSTANT INCREASING CONSTANT DECREASING INCREASING 315.2 additional daily steps 397.8 additional daily steps 136.3 additional daily steps (95% CI, 6 - 624.4 steps) p = .046 (95% CI, 89.2 - 706.4 steps) p = .01 (95% CI, 30.3 - 242.3 steps) p = .01 DECREASING 308.6 additional daily steps (95% CI, 0.1 - 617.1 steps) p = .05 7400 7400 7400 7275 7275 7275 7150 7150 7150 7025 7025 7025 6900 6900 6900 2nd week 3rd week 1st week
3. Cost-e ff ectiveness • For additional $1 paid, • Amount of money earned + 582.4 steps $15.48 CONSTANT CONSTANT + 107 steps $14.54 INCREASING INCREASING + 153.1 steps $14.67 DECREASING DECREASING
DISCUSSION
Summary Not only incentive size, but also incentive structure matters! • incentives significantly increased physical CONSTANT activity relative to all other conditions. - held for 1 week after the intervention & dissipated after then. • group performed equally as well as those CONTROL receiving a 20-fold greater incentive
Summary WHY constant incentive? • CONSTANT : easier to remember —> more salient and effective at promoting physical activity • Increasing Decreasing : confusing or unfair —> related ineffectiveness
Limitations • Dependent on participants’ device-wearing behaviors • Other physiological metrics might be more relevant to long- term health outcomes • Lack of demographic data for the population • Short intervention period, small incentive size compared with prior experiments. • Unanswered question: how to promote long-term changes?
What else?
Could prospect theory, loss aversion, and regret used to design an effective weight loss intervention?
Study Design • Main outcome: Weight loss after 16 weeks • Participants: 57 healthy participants with BMI 30-40 • Compared 2 different incentive groups & control group Intervention Follow-up 4 months 3 months
Study Design Goal: -16lb over 16 weeks Weigh-in control group Deposit contract group Lottery incentive group • opportunity to contribute $0.01 ~ • eligible for a daily lottery prize with • No incentives. $3.00 for each day (beginning of the an expected value of $3/day month) ( 0.01% $100 / 0.05% 10$) • received incentives for monthly weigh-in regardless of weight loss • refundable at the end of the month if • Receive money at the end of the they reach the goal month if they reach the goal • incentive: if deposit, +$3 day • Daily feedback about each day payoff • could earn $0 ~ $252 • Daily feedback “how much money they earned that day
Results control Deposit Lottery control Deposit Lottery 14 10 14lb 13.1lb 9.2lb 10.5 7.5 6.2lb 7 5 4.4lb 3.5 2.5 3.9lb 0 0 Weight loss Month 7 400 60 $378.5 52.6% 300 45 47% $272.8 200 30 100 15 $0.0 10.5% 0 0 Money earned Goal achieved
Discussions • Lost to follow-up rates were much lower than typical weight-loss studies • Weight loss improved immediate outcomes such as blood pressure, glycerin control, serum lipid levels etc • Still, substantial amounts of weight were regained.
Discussions • Rapid feedback about whether they • Even small reward and won money/ non-adherent punishments can have great participants: about whether they incentive value if they occur would have earned money immediately • Lottery provided frequent small • Motivated by experience of past payoffs and infrequent large rewards and the prospect of future payoffs . reward, and emotionally attracted to small probabilities of large rewards • Feedback about what they would • Desire to avoid regret have won had they been adherent
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