title: Validity of theFitbitactivity tracker for measuring steps in community-dwelling older adults.
abstract: BACKGROUND
  Commercially available activity monitors, such as theFitbit, may encourage physical activity. However, the accuracy of theFitbitin older adults remains unknown. This study aimed to determine (1) the criterion validity ofFitbitstep counts compared to visual count andActiGraphaccelerometer step counts and (2) the accuracy ofActiGraphstep counts compared to visual count in community-dwelling older people.
  
  
  METHODS
  Thirty-two community-dwelling adults aged over 60 woreFitbitandActiGraphdevices simultaneously during a 2 min walk test (2MWT) and then during waking hours over a 7-day period. A physiotherapist counted the steps taken during the 2MWT.
  
  
  RESULTS
  There was excellent agreement betweenFitbitand visually counted steps (intraclass correlation coefficient (ICC2,1)=0.88, 95% CI 0.76 to 0.94) from the 2MWT, and good agreement betweenFitbitandActiGraph(ICC2,1=0.66, 95% CI 0.41 to 0.82), and betweenActiGraphand visually counted steps (ICC2,1=0.60, 95% CI 0.33 to 0.79). There was excellent agreement between theFitbitandActiGraphin average steps/day over 7 days (ICC2,1=0.94, 95% CI 0.88 to 0.97). Percentage agreement was closest forFitbitsteps compared to visual count (mean 0%, SD 4%) and least forFitbitaverage steps/day compared to theActiGraph(mean 13%, SD 25%).
  
  
  CONCLUSIONS
  TheFitbitaccurately tracked steps during the 2MWT, but theActiGraphappeared to underestimate steps. There was strong agreement betweenFitbitandActiGraphcounted steps. TheFitbittracker is sufficiently accurate to be used among community-dwelling older adults to monitor and give feedback on step counts.
authors.affiliation: The George Institute for Global Health, Sydney Medical School, The University of Sydney , Sydney, New South Wales , Australia.
authors.forename: Serene S
authors.initials: SS
authors.lastname: Paul
authors.affiliation: The George Institute for Global Health, Sydney Medical School, The University of Sydney , Sydney, New South Wales , Australia.
authors.forename: Anne
authors.initials: A
authors.lastname: Tiedemann
authors.affiliation: The George Institute for Global Health, Sydney Medical School, The University of Sydney, Sydney, New South Wales, Australia; Faculty of Health Sciences, The University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Leanne M
authors.initials: LM
authors.lastname: Hassett
authors.affiliation: The George Institute for Global Health, Sydney Medical School, The University of Sydney , Sydney, New South Wales , Australia.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Ramsay
authors.affiliation: The George Institute for Global Health, Sydney Medical School, The University of Sydney , Sydney, New South Wales , Australia.
authors.forename: Catherine
authors.initials: C
authors.lastname: Kirkham
authors.affiliation: The George Institute for Global Health, Sydney Medical School, The University of Sydney , Sydney, New South Wales , Australia.
authors.forename: Sakina
authors.initials: S
authors.lastname: Chagpar
authors.affiliation: The George Institute for Global Health, Sydney Medical School, The University of Sydney , Sydney, New South Wales , Australia.
authors.forename: Catherine
authors.initials: C
authors.lastname: Sherrington
keywords: accelerometer; aged; pedometer; physical activity; validity