Effect of wearables on sleep in healthy individuals: a randomized crossover trial and validation study

Abstract

Study objectives: The purpose of this study was to determine whether a wearable sleep-tracker improves perceived sleep quality in healthy participants and to test whether wearables reliably measure sleep quantity and quality compared with polysomnography.

Methods: This study included a single-center randomized crossover trial of community-based participants without medical conditions or sleep disorders. A wearable device (WHOOP, Inc.) was used that provided feedback regarding sleep information to the participant for 1 week and maintained sleep logs versus 1 week of maintained sleep logs alone. Self-reported daily sleep behaviors were documented in sleep logs. Polysomnography was performed on 1 night when wearing the wearable. The Patient-Reported Outcomes Measurement Information System sleep disturbance sleep scale was measured at baseline, day 7 and day 14 of study participation.

Results: In 32 participants (21 women; 23.8 ± 5 years), wearables improved nighttime sleep quality (Patient-Reported Outcomes Measurement Information System sleep disturbance: B = -1.69; 95% confidence interval, -3.11 to -0.27; P = .021) after adjusting for age, sex, baseline, and order effect. There was a small increase in self-reported daytime naps when wearing the device (B = 3.2; SE, 1.4; P = .023), but total daily sleep remained unchanged (P = .43). The wearable had low bias (13.8 minutes) and precision (17.8 minutes) errors for measuring sleep duration and measured dream sleep and slow wave sleep accurately (intraclass coefficient, 0.74 ± 0.28 and 0.85 ± 0.15, respectively). Bias and precision error for heart rate (bias, -0.17%; precision, 1.5%) and respiratory rate (bias, 1.8%; precision, 6.7%) were very low compared with that measured by electrocardiogram and inductance plethysmography during polysomnography.

Conclusions: In healthy people, wearables can improve sleep quality and accurately measure sleep and cardiorespiratory variables.

Clinical trial registration: Registry: ClinicalTrials.gov; Name: Assessment of Sleep by WHOOP in Ambulatory Subjects; Identifier: NCT03692195.

Keywords: sleep; sleep loss; sleep quality; sleep tracker; wearable.

Figure 1. CONSORT diagram of flow pf participants through the randomized crossover clinical trial.

PSG = polysomnography.

Figure 2. Heart rate variability and strain.

Heart rate variability (top) and strain (a measure of physical activity derived from heart rate; bottom) are shown for women (green symbols) and men (red symbols). During the 7 days of wearing the device, heart rate variability measured by the device increased over time (top right; black symbols; P = .01), and there were no sex differences, whereas physical activity increased in men but not in women (bottom).