Measures of sleep and cardiac functioning during sleep using a multi-sensory commercially-available wristband in adolescents

• Accuracy of FitbitChargeHR™ to assess sleep and heart rate during sleep is tested.
• Fitbit device is reliable in detecting standard polysomnographic (PSG) metrics.
• Fitbit device performed well in detecting heart rate during sleep.
• Similar to standard actigraphy, Fitbit device had lower ability in detecting wake.
• FitbitChargeHR™ may be a valid alternative to PSG in healthy populations.

To validate measures of sleep and heart rate (HR) during sleep generated by a commercially-available activity tracker against those derived from polysomnography (PSG) in healthy adolescents. Sleep data were concurrently recorded using FitbitChargeHR™ and PSG, including electrocardiography (ECG), during an overnight laboratory sleep recording in 32 healthy adolescents (15 females; age, mean ± SD: 17.3 ± 2.5 years). Sleep and HR measures were compared between FitbitChargeHR™ and PSG using paired t-tests and Bland-Altman plots. Epoch-by-epoch analysis showed that FitbitChargeHR™ had high overall accuracy (91%), high sensitivity (97%) in detecting sleep, and poor specificity (42%) in detecting wake on a min-to-min basis. On average, FitbitChargeHR™ significantly but negligibly overestimated total sleep time by 8 min and sleep efficiency by 1.8%, and underestimated wake after sleep onset by 5.6 min (p < 0.05). Within FitbitChargeHR™ epochs of sleep, the average HR was 59.3 ± 7.5 bpm, which was significantly but negligibly lower than that calculated from ECG (60.2 ± 7.6 bpm, p < 0.001), with no change in mean discrepancies throughout the night. FitbitChargeHR™ showed good agreement with PSG and ECG in measuring sleep and HR during sleep, supporting its use in assessing sleep and cardiac function in healthy adolescents. Further validation is needed to assess its reliability over prolonged periods of time in ecological settings and in clinical populations.