Validity of Commercial Activity Trackers in Children With Congenital Heart Disease.

Background: Increasing physical activity levels is a high priority to optimize long-term health in children with congenital heart disease (CHD). Commercial activity trackers have been validated in adults and are increasingly used to measure and promote physical activity in pediatric populations, but they have not been validated in children.

Methods: In 30 children with CHD aged 10-18 years, we assessed the validity of physical activity form the wrist-based Fitbit Charge HR (Fitbit, San Francisco, CA) against hip-based ActiGraph (ActiGraph LLC, Pensacola, FL) accelerometers under free living conditions for 7 days. We assessed the association between devices using intraclass correlation coefficients (ICCs) and Bland-Altman plots. Receiver operating curves were used to identify Fitbit step cut points.

Results: There was a strong association between the 2 devices for daily steps across 138 analyzed person-days (ICC = 0.855; P < 0.001), but poorer agreement for time spent in physical activity intensities (ICCs < 0.7). Daily Fitbit steps of ≥ 12,500 identified meeting physical activity guidelines defined as ≥ 60 minutes of moderate-to-vigorous physical activity per day. Fitbit devices recorded more steps than accelerometers (-2242 steps per day, 95% limits of agreement of -7738 to 3253). Between-device differences were greater in boys vs girls. Fitbit devices were worn for longer than accelerometers (-36 minutes per day, 95% limits of agreement, -334 to 261), but overall differences in wear time explained little of the variance in step differences (7%, P = 0.048).

Conclusions: Commercial activity trackers provide opportunities to remotely monitor physical activity in children with CHD, but absolute values might differ from accelerometers. These findings are important because of the increasing emphasis on physical activity promotion and monitoring in children with cardiovascular risk factors.