'Minimal interventions' delivered via smartphone drive short-term health behavior changes

A new Stanford study found short-term daily activity increases stemming from four different approaches to smartphone-based prompts.
By Dave Muoio
03:49 pm

A new Stanford University-led study has found behavioral interventions such as activity reminders and education prompts delivered through a mobile app led to a significant increase in daily steps taken.

“The results of this study show that minimal interventions delivered in a digital format can have a significant effect on physical activity,” the researchers wrote in The Lancet Digital Health. “The sophistication of the intervention in this study seemed to have little impact on the effect: a simple, once daily prompt was as effective as a prompt to remind users to stand after one hour of sitting. Future studies should explore whether individualizing interventions could promote larger effects.”

While the study was conducted independently, some of the authors noted prior or ongoing relationships with device companies such as Apple, Fitbit, Verily and BioTelemetry; as well as with larger pharmaceutical and life sciences firms such as BMS-Pfizer, Merck, Bristol-Myers Squibb and Takeda.

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From late 2016 to mid-2018, researchers collected activity data from 1,075 study enrollees who completed the baseline week of data collection and at least one day of a measured intervention. Of these, 493 completed all four of the interventions.

Participants recorded a baseline activity level of 2,914 daily steps. Compared to that baseline, the greatest increase in activity come from prompts to visit the American Heart Association’s website (mean 319 step increase; p < .0001), and the smallest increase from more traditional “0,000 step” reminders (mean 226 step increase; p = .0026). Those receiving hourly prompts to stand increased their activity by a mean 267 steps (p = .0003), while those receiving daily coaching messages based on their individual activity patterns recorded a mean 254 step increase (p =.0006).

However, no single intervention was significantly more effective than the others, they wrote, and the positive results persisted when restricting analysis to the 493 participants who had completed all four of the interventions.

Additionally, a secondary analysis incorporating smartwatch activity data showed similar, albeit slightly greater, increases in these trends. The researchers observed no significant effects related to participants’ sleep duration, sleep quality, time spent walking per day or self-reported happiness.


The researchers enrolled 2,783 adult participants of the broader MyHeart Counts study, all of whom were required to own an iPhone to download the MyHeart Counts clinical research smartphone app. Upon consent, these subjects underwent one week of baseline monitoring and then were assigned to one of five “clusters” based on their activity trends.

These participants were then assigned the four interventions in a random order, with each intervention delivered over sequential one-week periods. Each intervention was delivered via daily smartphone messages, with participants receiving “electronic badges” as rewards for completing each step.

While mean daily step count changes from baseline as measured by in Apple’s HealthKit mobile app was the primary outcome of interest, the researchers also collected data on sleep habits, self-reported happiness related to an intervention, and similar activity behavior data as measured by a user’s smartwatch.


A number of studies have looked to smartphones as a tool for monitoring changes in daily activity as well as delivering behavioral interventions. HealthKit and ResearchKit each have played a major role in the former for Apple’s devices, and a study published late last year gave high marks to the iPhone’s built-in step measurement capabilities (although walking distance measurements were a bit off). And there’s little shortage of mobile disease management programs that generate and deliver personalized notifications intended to influence healthy behavior.

Admittedly though, researchers are increasingly looking to consumer smartwatches for their device-driven monitoring needs. Apple itself has a number of clear number of examples in this regard, ranging from the recently concluded Apple Heart Study to new efforts focused on physical activity, sound exposure and more.


“This study demonstrates the feasibility of using smartphones to do a crossover randomized trial entirely in the digital domain,” the researchers wrote. “The results suggest daily coaching delivered via a smartphone is effective in the short term at modestly increasing daily step count compared with baseline. These findings are consistent with previous studies that have shown that smartphone interventions can increase physical activity.”


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