Digital Randomized Controlled Trial of Physical Activity Interventions (A Substudy of the MyHeart Counts Cardiovascular Health Study)

Background: Smartphone applications may enable interventions to increase physical activity but this has limited evidence in randomized trials. Objectives: The MyHeart Counts Cardiovascular Health study (MHC) is a smartphone-based longitudinal research study aimed at elucidating the determinants of cardiovascular health. Among MHC participants, we performed a randomized controlled trial to investigate the response to four different physical activity coaching interventions on the primary outcome of change in daily step count. Secondary outcomes included life satisfaction, 6-minute walk distance, and sleep quality. Methods: The trial was completed entirely using personal smartphones: participants were digitally consented, the interventions were delivered via the device, and measurements of the primary and secondary outcomes were collected from smartphone sensors. Participants were enrolled from December 12, 2016 to June 6, 2018 and followed for up to 5 weeks. Participants completed the trial through the MyHeart Counts phone app in a free-living setting. All adults over 18 years of age with access to a smartphone (Apple iPhone, version 5S or later) were eligible to participate. After one week of baseline measurements, participants (n=2783) were randomized to a sequence of four, week-long interventions delivered in random order. Interventions consisted of either daily prompts to complete 10,000 steps (completed by n=853); hourly prompts to stand following a full hour of sitting (completed by n=879); instructions to read the guidelines from the American Heart Association website (completed by n=868); and e-coaching based upon the individual's personal activity patterns from the baseline week of data collection (completed by n=896). Results: 2783 participants consented to enroll in the coaching study, of whom 1075 completed the baseline week of data collection and at least one of the four interventions. 493 individuals completed the full set of assigned interventions. All four interventions were found effective at modestly increasing daily step count by a mean of 266 ±75 steps from a baseline mean of 2958±69 steps (p=0.003). Intervention-specific step increases were: 319±74 steps (p<0.001) for the prompt to read the AHA Website, 267±74 steps (p<0.001) for the hourly stand prompt, 254±73 steps (p<0.001) for the participant-specific prompts, and 226±75 steps (p=<0.01 versus baseline) for the prompt to complete the daily 10,000 step goal. No significant effect of the interventions on any pre-specified secondary outcome was observed. Conclusions: The results indicate that four smartphone-based physical activity coaching interventions significantly increased daily physical activity in a short-term, randomized, controlled trial completed entirely using personal smartphones. Trial Registration: ClinicalTrials.gov Identifier NCT03090321 Funding Statement: The Division of Cardiovascular Medicine, Department of Medicine, Stanford University, received in-kind (software development) support from Apple Inc for the launch version of MHC. Software development since launch was funded by the Stanford Data Science Initiative. Steven Hershman is supported by The Division of Cardiovascular Medicine, Department of Medicine. Dr Sharma reports research grant support from the AHA Strategically Focused Research Network - Heart Failure (16SFRN30180010), Alberta Innovates Health Solution Clinician Scientist fellowship. Declaration of Interests: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr. McConnell is an employee of Verily Life Sciences LLC. Dr Harrington is on the board of directors for Scanadu Inc (which is privately held) but reported receiving no consulting fees and reported having stock options with no current value. Dr Sharma reports research support from Roche Diagnostics, Takeda, BMS-Pfizer, and the Canadian Cardiovascular Society Bayer Vascular award. The remaining authors have nothing to disclose. Ethics Approval Statement: Ethical review and approval of the study was obtained from Stanford University’s Research Compliance Office (Protocol #IRB-31409).