Evaluating the Carrot Rewards app, a population-level incentive-based intervention promoting step counts across two Canadian provinces: a quasi-experimental study (Preprint)
Authors: Mitchell Marc , White Lauren , Lau Erica , Leahey Tricia , Adams Marc , Faulkner Guy 
Published: January 2018

BACKGROUND

The Carrot Rewards application (‘app’) was developed as part of an innovative public-private partnership to reward Canadians with loyalty points, exchangeable for retail goods, travel rewards and groceries, for engaging in healthy behaviors such as walking.

OBJECTIVE

The purpose of this study was to examine whether a multi-component intervention including goal setting, graded tasks, biofeedback and very small incentives tied to daily step goal achievement (assessed by built-in smartphone accelerometers) could increase physical activity in two Canadian provinces, British Columbia (BC) and Newfoundland and Labrador (NL).

METHODS

A 12-week quasi-experimental (single group pre/post) study was conducted. Among eligible participants (n=78,882), 44.39% (n=35,014) enrolled in the Carrot Rewards “Steps” walking program during the recruitment period (June 13th – July 10th 2016). During the two-week baseline (or ‘run-in’) period, mean steps/day were calculated for participants. Thereafter, participants earned incentives in the form of loyalty points (worth $0.04 CAD) every day they reached their personalized daily step goal (i.e. baseline mean + 1,000 steps = level of first daily step goal). Participants earned additional points (worth $0.40 CAD) for meeting their step goal 10+ non-consecutive times in a 14-day period (called a “Step Up Challenge”). Participants could earn up to $5.00 CAD during the 12-week evaluation period. Upon meeting the 10-day contingency, participants could increase their daily goal by 500 steps, with the objective of gradually increasing the number of steps participants take each day by 3,000. Only participants with five or more valid days (days with step counts between 1,000 and 40,000) during the baseline period were included in the analysis (n=32,229).The primary study outcome was mean steps/day (by week), and was analyzed using linear mixed-effects models.

RESULTS

Of the 32,229 participants with valid baseline data, the mean age was 33.7  11.6 years and 66.11% (21,306/32,229) were female. The mean daily step count at baseline was 6,511.22. Just over half of users (50.69%, 16,336/32,229) were categorized as “physically inactive”, accumulating less than 5,000 daily steps at baseline. Results from the mixed-effects models revealed statistically significant increases in mean daily step counts when comparing baseline with each Study Week (P<.0001). Compared to baseline, participants walked 115.70 more steps (95% CI: 74.59,156.81; P<.0001) at Study Week 12. Users classified as “high engagers” (app engagement above the sample median; 48.13%, 15,511/32,229) in BC and NL walked 738.70 (95% CI: 673.81, 803.54; P<.0001) and 346.00 (95% CI: 239.26, 452.74; P<.0001) more steps, respectively. Among physically inactive, high engagers (21.08%; 7,022/32,229) an average increase of 1,224.66 steps per day (95% CI: 1160.69, 1288.63; P<.0001) was observed. Effect sizes were modest

CONCLUSIONS

Providing very small but immediate rewards for personalized daily step goal achievement as part of a multi-component intervention increased daily step counts on a population-scale, especially for physically inactive individuals and individuals who engaged more with the walking program. Positive effects in both BC and NL provide evidence of replicability.