title: Feasibility of Obtaining Measures of Lifestyle From a Smartphone App: The MyHeart Counts Cardiovascular Health Study.
abstract: Studies have established the importance of physical activity and fitness, yet limited data exist on the associations between objective, real-world physical activity patterns, fitness, sleep, and cardiovascular health.
  
  
  
  To assess the feasibility of obtaining measures of physical activity, fitness, and sleep from smartphones and to gain insights into activity patterns associated with life satisfaction and self-reported disease.
  
  
  
  The MyHeart Counts smartphone app was made available in March 2015, and prospective participants downloaded the free app between March and October 2015. In this smartphone-based study of cardiovascular health, participants recorded physical activity, filled out health questionnaires, and completed a 6-minute walk test. The app was available to download within the United States.
  
  
  
  The feasibility of consent and data collection entirely on a smartphone, the use of machine learning to cluster participants, and the associations between activity patterns, life satisfaction, and self-reported disease.
  
  
  
  From the launch to the time of the data freeze for this study (March to October 2015), the number of individuals (self-selected) who consented to participate was 48 968, representing all 50 states and the District of Columbia. Their median age was 36 years (interquartile range, 27-50 years), and 82.2% (30 338 male, 6556 female, 10 other, and 3115 unknown) were male. In total, 40 017 (81.7% of those who consented) uploaded data. Among those who consented, 20 345 individuals (41.5%) completed 4 of the 7 days of motion data collection, and 4552 individuals (9.3%) completed all 7 days. Among those who consented, 40 017 (81.7%) filled out some portion of the questionnaires, and 4990 (10.2%) completed the 6-minute walk test, made available only at the end of 7 days. The Heart Age Questionnaire, also available after 7 days, required entering lipid values and age 40 to 79 years (among 17 245 individuals, 43.1% of participants). Consequently, 1334 (2.7%) of those who consented completed all fields needed to compute heart age and a 10-year risk score. Physical activity was detected for a mean (SD) of 14.5% (8.0%) of individuals' total recorded time. Physical activity patterns were identified by cluster analysis. A pattern of lower overall activity but more frequent transitions between active and inactive states was associated with equivalent self-reported cardiovascular disease as a pattern of higher overall activity with fewer transitions. Individuals' perception of their activity and risk bore little relation to sensor-estimated activity or calculated cardiovascular risk.
  
  
  
  A smartphone-based study of cardiovascular health is feasible, and improvements in participant diversity and engagement will maximize yield from consented participants. Large-scale, real-world assessment of physical activity, fitness, and sleep using mobile devices may be a useful addition to future population health studies.
authors.affiliation: Department of Medicine, Stanford University, Stanford, California2Division of Cardiovascular Medicine, Department of Medicine, Stanford University, Stanford, California3Verily Life Sciences LLC, South San Francisco, California.
authors.forename: Michael V
authors.initials: MV
authors.lastname: McConnell
authors.affiliation: Department of Medicine, Stanford University, Stanford, California2Division of Cardiovascular Medicine, Department of Medicine, Stanford University, Stanford, California.
authors.forename: Anna
authors.initials: A
authors.lastname: Shcherbina
authors.affiliation: Department of Medicine, Stanford University, Stanford, California2Division of Cardiovascular Medicine, Department of Medicine, Stanford University, Stanford, California.
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Pavlovic
authors.affiliation: Department of Genetics, Stanford University, Stanford, California.
authors.forename: Julian R
authors.initials: JR
authors.lastname: Homburger
authors.affiliation: Department of Medicine, Stanford University, Stanford, California2Division of Cardiovascular Medicine, Department of Medicine, Stanford University, Stanford, California.
authors.forename: Rachel L
authors.initials: RL
authors.lastname: Goldfeder
authors.affiliation: Department of Medicine, Stanford University, Stanford, California5Stanford Center for Cardiovascular Innovation, Stanford University, Stanford, California.
authors.forename: Daryl
authors.initials: D
authors.lastname: Waggot
authors.affiliation: Department of Medicine, Stanford University, Stanford, California2Division of Cardiovascular Medicine, Department of Medicine, Stanford University, Stanford, California6Stanford Center for Biomedical Ethics, Stanford University, Stanford, California.
authors.forename: Mildred K
authors.initials: MK
authors.lastname: Cho
authors.affiliation: Stanford Prevention Research Center, Stanford University, Stanford, California.
authors.forename: Mary E
authors.initials: ME
authors.lastname: Rosenberger
authors.affiliation: Stanford Prevention Research Center, Stanford University, Stanford, California.
authors.forename: William L
authors.initials: WL
authors.lastname: Haskell
authors.affiliation: Department of Medicine, Stanford University, Stanford, California2Division of Cardiovascular Medicine, Department of Medicine, Stanford University, Stanford, California.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Myers
authors.affiliation: Department of Medicine, Stanford University, Stanford, California2Division of Cardiovascular Medicine, Department of Medicine, Stanford University, Stanford, California.
authors.forename: Mary Ann
authors.initials: MA
authors.lastname: Champagne
authors.affiliation: Stanford Sleep Center, Stanford University, Palo Alto, California.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Mignot
authors.affiliation: Big Data Institute, Nuffield Department of Population Health, University of Oxford, Oxford, England.
authors.forename: Martin
authors.initials: M
authors.lastname: Landray
authors.affiliation: Oxford Institute of Biomedical Engineering, Oxford, England.
authors.forename: Lionel
authors.initials: L
authors.lastname: Tarassenko
authors.affiliation: Department of Medicine, Stanford University, Stanford, California2Division of Cardiovascular Medicine, Department of Medicine, Stanford University, Stanford, California.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Harrington
authors.affiliation: Department of Medicine, Stanford University, Stanford, California2Division of Cardiovascular Medicine, Department of Medicine, Stanford University, Stanford, California5Stanford Center for Cardiovascular Innovation, Stanford University, Stanford, California.
authors.forename: Alan C
authors.initials: AC
authors.lastname: Yeung
authors.affiliation: Department of Medicine, Stanford University, Stanford, California2Division of Cardiovascular Medicine, Department of Medicine, Stanford University, Stanford, California4Department of Genetics, Stanford University, Stanford, California.
authors.forename: Euan A
authors.initials: EA
authors.lastname: Ashley
mesh_terms: D000328:Adult; D000368:Aged; D000072599:Cardiorespiratory Fitness / Q000502:physiology; D002320:Cardiovascular Physiological Phenomena; D015444:Exercise / Q000502:physiology*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008019:Life Style; D008297:Male; D008875:Middle Aged; D063731:Mobile Applications; D011446:Prospective Studies; D012890:Sleep; D011795:Surveys and Questionnaires; D017216:Telemedicine / Q000295:instrumentation*