Validation of a nonwearable device in healthy adults with normal and short sleep durations

Abstract

Study Objectives: To determine the accuracy of early and newer versions of a nonwearable sleep tracking device relative to polysomnography and actigraphy, under conditions of normal and restricted sleep duration. Methods: Participants were 35 healthy adults (mean age = 18.97; standard deviation = 0.95 years; 77.14% female; 42.86% White). In a controlled sleep laboratory environment, we randomly assigned participants to go to bed at 10:30 PM (normal sleep) or 1:30 AM (restricted sleep), setting lights-on at 7:00 AM. Sleep was measured using polysomnography, wristband actigraphy (the Philips Respironics Actiwatch Spectrum Plus), self-report, and an early or newer version of a nonwearable device that uses a sensor strip to measure movement, heart rate, and breathing (the Apple, Inc. Beddit). We tested accuracy against polysomnography for total sleep time, sleep efficiency, sleep onset latency, and wake after sleep onset. Results: The early version of the nonwearable device (Beddit 3.0) displayed poor reliability (intraclass correlation coefficient [ICC] < 0.30). However, the newer nonwearable device (Beddit 3.5) yielded excellent reliability with polysomnography for total sleep time (ICC = 0.998) and sleep efficiency (ICC = 0.98) across normal and restricted sleep conditions. Agreement was also excellent for the notoriously difficult metrics of sleep onset latency (ICC = 0.92) and wake after sleep onset (ICC = 0.92). This nonwearable device significantly outperformed clinical-grade actigraphy (ICC between 0.44 and 0.96) and self-reported sleep measures (ICC < 0.75). Conclusions: A nonwearable device showed better agreement than actigraphy with polysomnography outcome measures. Future work is needed to test the validity of this device in clinical populations.