Personalized digital behavior interventions increase short term physical activity: a randomized control crossover trial substudy of the MyHeart Counts Cardiovascular Health study

Background: Physical activity is strongly protective against the development of chronic diseases associated with aging. We previously demonstrated that digital interventions delivered through a smartphone app can increase short-term physical activity. Our randomized crossover trial has continued to digitally enroll participants, allowing increasing statistical power for greater precision in subsequent analyses. Methods: We offered enrollment to adults aged >=18 years with access to an iPhone and the MyHeart Counts app. After completion of a 1-week baseline period, e-consented participants were randomly allocated to four 7-day interventions. Interventions consisted of: 1) daily personalized e-coaching based on the individuals baseline activity patterns, 2) daily prompts to complete 10,000 steps, 3) hourly prompts to stand following inactivity, and 4) daily instructions to read guidelines from the American Heart Association website. The trial was completed in a free-living setting, where neither the participants or investigators were blinded to the intervention. The primary outcome was change in mean daily step count from baseline for each of the four interventions, assessed in a modified intention-to-treat analysis. This trial is registered with ClinicalTrials.gov, [NCT03090321][1]. Findings: Between January 1, 2017 and April 1, 2022, 4500 participants consented to enroll in the trial, of whom 2458 completed 7-days of baseline monitoring (mean daily steps 4232+/-73) and at least one day of one of the four interventions. The greater statistical power afforded by continued passive enrollment revealed that e-coaching prompts, tailored to an individual, increased step count significantly more than other interventions (402+/-71 steps, P=7.1x10-8). Interpretation: Digital studies can continuously recruit participants in a cost-effective manner, allowing for new insights provided by increased statistical power and refinement of prior signals. Here, we show that digital interventions tailored to an individual are effective in increasing short-term physical activity in a free-living cohort. Funding: Stanford Data Science Initiative and Catalyst Program, Apple, Google ### Competing Interest Statement M.T.W. reports grants and personal fees from Verily, Myokardia, and ArrayBio, and consultancy fees from BioTelemetry, outside the submitted work. E.A.A. reports advisory board fees from Apple and Foresite Labs. E.A.A. has ownership interest in Nuevocor, DeepCell, and Personalis, outside the submitted work. E.A.A. is a board member of AstraZeneca. E.A.A. and C.M.M. have ownership interest in SVEXA, outside of the submitted work. M.V.M. is an employee at identifeye HEALTH, a previous employee at Google/Fitbit (until 2022), a member of the medical advisory board of 4Catalyzer Corp, and on the board of directors of the National Fitness Foundation. S.G.H. is an employee of Biofourmis. D.S.K. is supported by the Wu-Tsai Human Performance Alliance. The remainder of authors report no potential conflicts of interest. ### Clinical Trial NCT03090321 ### Funding Statement Stanford Data Science Initiative and Catalyst Program, Apple, Google ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Ethical approval for the study was obtained from the Stanford University Research Compliance Office I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes The data that support the findings of this study are available on request from the corresponding authors, DSK and EAA. The data are not publicly available due to the Health Insurance Portability and Accountability Act of 1996 (HIPAA). [1]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT03090321&atom=%2Fmedrxiv%2Fearly%2F2023%2F04%2F11%2F2023.04.09.23287650.atom