Sleep Tracking of a Commercially Available Smart Ring and Smartwatch Against Medical-Grade Actigraphy in Everyday Settings: Instrument Validation Study

Abstract

Background: Assessment of sleep quality is essential to address poor sleep quality and understand changes. Owing to the advances in the Internet of Things and wearable technologies, sleep monitoring under free-living conditions has become feasible and practicable. Smart rings and smartwatches can be employed to perform mid- or long-term home-based sleep monitoring. However, the validity of such wearables should be investigated in terms of sleep parameters. Sleep validation studies are mostly limited to short-term laboratory tests; there is a need for a study to assess the sleep attributes of wearables in everyday settings, where users engage in their daily routines.

Objective: This study aims to evaluate the sleep parameters of the Oura ring along with the Samsung Gear Sport watch in comparison with a medically approved actigraphy device in a midterm everyday setting, where users engage in their daily routines.

Methods: We conducted home-based sleep monitoring in which the sleep parameters of 45 healthy individuals (23 women and 22 men) were tracked for 7 days. Total sleep time (TST), sleep efficiency (SE), and wake after sleep onset (WASO) of the ring and watch were assessed using paired t tests, Bland-Altman plots, and Pearson correlation. The parameters were also investigated considering the gender of the participants as a dependent variable.

Results: We found significant correlations between the ring's and actigraphy's TST (r=0.86; P<.001), WASO (r=0.41; P<.001), and SE (r=0.47; P<.001). Comparing the watch with actigraphy showed a significant correlation in TST (r=0.59; P<.001). The mean differences in TST, WASO, and SE of the ring and actigraphy were within satisfactory ranges, although there were significant differences between the parameters (P<.001); TST and SE mean differences were also within satisfactory ranges for the watch, and the WASO was slightly higher than the range (31.27, SD 35.15). However, the mean differences of the parameters between the watch and actigraphy were considerably higher than those of the ring. The watch also showed a significant difference in TST (P<.001) between female and male groups.

Conclusions: In a sample population of healthy adults, the sleep parameters of both the Oura ring and Samsung watch have acceptable mean differences and indicate significant correlations with actigraphy, but the ring outperforms the watch in terms of the nonstaging sleep parameters.

Keywords: actigraphy; sleep; smart ring; smartwatch; wearable technology.

Figure 1

Watch data processing pipeline.

Figure 2

Bland-Altman plots for total sleep time, sleep efficiency, and wake after sleep onset gathered by the Oura ring and the actigraphy device. Subjects’ actigraphy minus Oura ring discrepancies on sleep parameters (y-axis) are plotted compared with actigraphy (x-axis). Biases, upper, and lower agreement limits are marked. In addition, the satisfactory ranges are plotted as the dashed lines. SE: sleep efficiency; TST: total sleep time; WASO: wake after sleep onset.

Figure 3

Bland-Altman plots for total sleep time, sleep efficiency, and wake after sleep onset gathered by the Samsung watch and the actigraphy device. Subjects’ actigraphy minus Samsung watch discrepancies on sleep parameters (y-axis) are plotted compared with actigraphy (x-axis). Biases, upper, and lower agreement limits are marked. In addition, the satisfactory ranges are plotted as the dashed lines. SE: sleep efficiency; TST: total sleep time; WASO: wake after sleep onset.

Figure 4

Bland-Altman plot for sleep onset latency estimated by the Oura ring. SOL: sleep onset latency.

Figure 5

Bland-Altman plot for sleep onset latency estimated by the Samsung watch. SOL: sleep onset latency.