Activity trackers disappoint in randomised trial
medwireNews: Wearing activity monitors does not lead to improved health outcomes, despite a modest increase in wearers’ activity levels, shows a large randomised trial.
The trial also assessed the effect of financial incentives, and found that, while these initially boosted people’s commitment to increasing their activity levels, stopping the incentive was counterproductive, with activity falling to less than that of people not offered a financial incentive.
The author of an accompanying commentary, Courtney Monroe (University of South Carolina, Columbia, USA), notes that financial incentives are an extrinsic motivator, and “might undermine or stifle the chance to develop intrinsic motivation, which is a strong predictor of physical activity adherence”.
She writes in The Lancet Diabetes & Endocrinology: “It is clear that although wearables have the potential to be an integral part of physical activity promotion efforts, additional research is needed to determine how to best foster device engagement.”
Eric Finkelstein (Duke-NUS Medical School, Singapore) and co-workers randomly divided the 800 study participants into four groups, but gave all of them educational leaflets about the importance of increasing their activity levels, plus sealed accelerometers to wear.
Over the first 6 months of the trial, one group was supplied with a Fitbit (San Francisco, California, USA) and also given a financial incentive (Singapore $15 for logging 50,000–70,000 steps/week; $30 for more). This group had the largest increase in moderate-to-vigorous physical activity (MVPA), logging an additional 13 minutes per week relative to at baseline and an additional 29 minutes versus the control participants, who did not receive a Fitbit.
Participants rewarded with charity donations on their behalf logged an additional 21 minutes per week of MVPA versus the controls, and those given a Fitbit with no incentives logged an additional 16 minutes, neither of which were statistically significant.
But at 6 months the incentives were halted, resulting in quite different findings at 12 months. The additional MVPA in the cash incentive group versus the control group had fallen to a nonsignificant 15 minutes per week, whereas that in the charity donation and Fitbit-only groups had risen to 32 and 37 minutes, respectively, which were both significant.
However, these results represented a small proportion of participants; 40% had stopped using the Fitbit by 6 months and 90% by 12 months.
Furthermore, at no time did the researchers find any differences between the groups in the health outcomes of weight, blood pressure, non-exercise testing for cardiorespiratory fitness, and maximum oxygen consumption. They attribute this to the rather small increase in activity – even participants offered cash incentives averaged only an additional 4 minutes per day at 6 months.
Monroe nonetheless believes the study to be important, saying: “Opportunities to continue integrating behavioural economics, wearables, and other evidence-based behaviour change components abound with potentially far-reaching implications.”
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