Objectives: Wearable fitness devices are increasingly used by the general population, with new applications being proposed and designed for healthy adults as well as adults with chronic diseases. Fewer, if any, studies of these devices have been conducted in healthy adolescents and teenagers, especially over a long period of time. The goal of this work was to document the successes and challenges involved in 5 years of a wearable fitness device use in a pediatric case study.

Materials and Methods: Comparison of five years of step counts and minutes asleep from a teenaged girl and her father.

Results: At 60 months, this may be the longest reported pediatric study involving a wearable fitness device, and the first simultaneously involving a parent and a child. We find step counts to be significantly higher for both the adult and teen on school/work days, along with less sleep. The teen walked significantly less towards the end of the 5 year study. Surprisingly, many of the adult’s and teen’s sleeping and step counts were correlated, possibly due to coordinated behaviors.

Discussion: We end with several recommendations for pediatricians and device manufacturers, including the need for constant adjustments of stride length and calorie counts as teens are growing.

Conclusion: With periodic adjustments for growth, this pilot study shows these devices can be used for more accurate and consistent measurements in adolescents and teenagers over longer periods of time, to potentially promote healthy behaviors.

Ethics: Two authors (including the lead author) collected their own data as citizen-scientist subjects, with their own devices that they obtained, initiated the analyses, then approached the Stanford investigators to enhance the analyses, and both of these subjects contributed to writing this manuscript.  The two data contributors joined Stanford University research protocol 56378 approved by the Stanford University Institutional Review Board, specifically allowing participants at or over age 13 years to share their past and current Fitbit measurement data with Stanford investigators for research purposes, with informed consent.

Two Fitbit One devices were purchased (Amazon.com) on January 1, 2013 and activated shortly thereafter. The Fitbit One was designed to track steps walked along with pace, stairs climbed, sleep duration and activity.  Two participants (and co-authors here) simultaneously started to use the devices to track these measurements.  The female participant started use at age 10 years and 4 months, and continued through her teenage years.  The adult male participant (father of the younger individual) started use at age 43 years and 9 months.  Neither had any significant prior medical history at the initiation of use.  Both intended the use of these devices for improving and maintaining general health and wellness.  The adult also intended to use the device to increase his walking and help in weight loss.  While these devices (or their subsequent versions) have still been in use since January 1, 2013, this analysis only covers the 60 months of use after a pattern of regular consistent use was seen, starting on June 1, 2013.  In June 2018, both participants elected to study their data together for research.

Fitbit enables the downloading of raw level device data, by registering through their Application Programming Interface (API).  Using the API ID number that Fitbit provided, a short program was written in R to access the Fitbit data, serially downloading blocks of daily step and sleep data representing every 100 days, to cover the entire 60 months. 

No outlier measurements were removed.  Sleep amounts in minutes are assigned to the wake up day.  Weekend nights were defined as those leading into a Saturday or Sunday, which are days with no school.  School days were defined as weekdays that were not within a set of five long holiday breaks: one week mid-winter break in February, one week spring break in March or April, ten week summer break in June-August, Thanksgiving one week break in November, and two week winter break between December and January.