Validation of a Consumer Sleep Wearable Device With Actigraphy and Polysomnography in Adolescents Across Sleep Opportunity Manipulations

Abstract

Study objectives: To compare the quality and consistency in sleep measurement of a consumer wearable device and a research-grade actigraph with polysomnography (PSG) in adolescents.

Methods: Fifty-eight healthy adolescents (aged 15-19 years; 30 males) underwent overnight PSG while wearing both a Fitbit Alta HR and a Philips Respironics Actiwatch 2 (AW2) for 5 nights, with either 5 hours or 6.5 hours time in bed (TIB) and for 4 nights with 9 hours TIB. AW2 data were evaluated using two different wake and immobility thresholds. Discrepancies in estimated total sleep time (TST) and wake after sleep onset (WASO) between devices and PSG, as well as epoch-by-epoch agreements in sleep/wake classification, were assessed. Fitbit-generated sleep staging was compared to PSG.

Results: Fitbit and AW2 under default settings similarly underestimated TST and overestimated WASO (TST: medium setting (M10) ≤ 38 minutes, Fitbit ≤ 47 minutes; WASO: M10 ≤ 38 minutes; Fitbit ≤ 42 minutes). AW2 at the high motion threshold setting provided readings closest to PSG (TST: ≤ 12 minutes; WASO: ≤ 18 minutes). Sensitivity for detecting sleep was ≥ 90% for both wearable devices and further improved to 95% by using the high threshold (H5) setting for the AW2 (0.95). Wake detection specificity was highest in Fitbit (≥ 0.88), followed by the AW2 at M10 (≥ 0.80) and H5 thresholds (≤ 0.73). In addition, Fitbit inconsistently estimated stage N1 + N2 sleep depending on TIB, underestimated stage N3 sleep (21-46 min), but was comparable to PSG for rapid eye movement sleep. Fitbit sensitivity values for the detection of N1 + N2, N3 and rapid eye movement sleep were ≥ 0.68, ≥ 0.50, and ≥ 0.72, respectively.

Conclusions: A consumer-grade wearable device can measure sleep duration as well as a research actigraph. However, sleep staging would benefit from further refinement before these methods can be reliably used for adolescents.

Clinical trial registration: Registry: ClinicalTrials.gov; Title: The Cognitive and Metabolic Effects of Sleep Restriction in Adolescents; Identifier: NCT03333512; URL: https://ichgcp.net/clinical-trials-registry/NCT03333512.

Citation: Lee XK, Chee NIYN, Ong JL, Teo TB, van Rijn E, Lo JC, Chee MWL. Validation of a consumer sleep wearable device with actigraphy and polysomnography in adolescents across sleep opportunity manipulations. J Clin Sleep Med. 2019;15(9):1337-1346.

Keywords: Fitbit; actigraphy; adolescent sleep; polysomnography.

© 2019 American Academy of Sleep Medicine.

Figures

Figure 1. Bland-Altman plots for total sleep time and wake after sleep onset.

Bland-Altman plots, in minutes, of (A) total sleep time and (B) wake after sleep onset. Red, green, and blue points represent data collected from the 5-hour, 6.5-hour, and 9-hour time in bed conditions respectively. Solid lines and bolded numbers represent the mean biases of each recording, whereas dashed lines and regular numbers represent 1.96 standard deviation limits of agreement. H5 = Actiwatch 2 high wake threshold with 5 immobile minutes for sleep onset and end, M10 = Actiwatch 2 medium wake threshold with 10 immobile minutes for sleep onset and end, PSG = polysomnography.

Figure 2. Bland-Altman plots for sleep stages.

Bland-Altman plots, in minutes, of (A) stage N1 + N2 sleep (light sleep), (B) stage N3 sleep (deep sleep), and (C) REM sleep. Red, green, and blue points represent data collected from the 5-hour, 6.5-hour, and 9-hour time in bed conditions, respectively. Solid lines and bold numbers represent the mean biases of each recording, whereas dashed lines and regular numbers represent 1.96 standard deviation limits of agreement. H5 = Actiwatch 2 high wake threshold with 5 immobile minutes for sleep onset and end, M10 = Actiwatch 2 medium wake threshold with 10 immobile minutes for sleep onset and end, PSG = polysomnography, REM = rapid eye movement.