Validity of Two Consumer Multisport Activity Tracker and One Accelerometer against Polysomnography for Measuring Sleep Parameters and Vital Data in a Laboratory Setting in Sleep Patients

Abstract

Two commercial multisport activity trackers (Garmin Forerunner 945 and Polar Ignite) and the accelerometer ActiGraph GT9X were evaluated in measuring vital data, sleep stages and sleep/wake patterns against polysomnography (PSG). Forty-nine adult patients with suspected sleep disorders (30 males/19 females) completed a one-night PSG sleep examination followed by a multiple sleep latency test (MSLT). Sleep parameters, time in bed (TIB), total sleep time (TST), wake after sleep onset (WASO), sleep onset latency (SOL), awake time (WASO + SOL), sleep stages (light, deep, REM sleep) and the number of sleep cycles were compared. Both commercial trackers showed high accuracy in measuring vital data (HR, HRV, SpO2, respiratory rate), r > 0.92. For TIB and TST, all three trackers showed medium to high correlation, r > 0.42. Garmin had significant overestimation of TST, with MAE of 84.63 min and MAPE of 25.32%. Polar also had an overestimation of TST, with MAE of 45.08 min and MAPE of 13.80%. ActiGraph GT9X results were inconspicuous. The trackers significantly underestimated awake times (WASO + SOL) with weak correlation, r = 0.11−0.57. The highest MAE was 50.35 min and the highest MAPE was 83.02% for WASO for Garmin and ActiGraph GT9X; Polar had the highest MAE of 21.17 min and the highest MAPE of 141.61% for SOL. Garmin showed significant deviations for sleep stages (p < 0.045), while Polar only showed significant deviations for sleep cycle (p = 0.000), r < 0.50. Garmin and Polar overestimated light sleep and underestimated deep sleep, Garmin significantly, with MAE up to 64.94 min and MAPE up to 116.50%. Both commercial trackers Garmin and Polar did not detect any daytime sleep at all during the MSLT test. The use of the multisport activity trackers for sleep analysis can only be recommended for general daily use and for research purposes. If precise data on sleep stages and parameters are required, their use is limited. The accuracy of the vital data measurement was adequate. Further studies are needed to evaluate their use for medical purposes, inside and outside of the sleep laboratory. The accelerometer ActiGraph GT9X showed overall suitable accuracy in detecting sleep/wake patterns.

Keywords: actigraphy; mHealth; polysomnography; self-tracking; sleep; validity; wearables.

Figure 1

Bland–Altman plots of sleep parameters (n = 49). TIB = time in bed, TST = total sleep time, Awake = awake time (WASO + SOL), WASO = wake after sleep onset, SOL = sleep onset latency (all expressed in minutes), SE = sleep efficiency (in %). x-axis represents the mean values of the device and PSG; y-axis represents the differences between the PSG and the device; dashed black line represents the upper and lower limit of agreement (mean +/− 1.96 SD); solid red line represents the mean value of difference; solid blue line represents the trend; shaded green area represents 95% CI (confidence interval) of mean difference.

Figure 2

Boxplot analysis of calculated deviation in sleep parameters, Garmin, Polar and ActiGraph GT9X against the gold standard PSG (n = 49), TIB = time in bed, TST = total sleep time, Awake = awake time (WASO + SOL), WASO = wake after sleep onset, SOL = sleep onset latency (all expressed in minutes); the x represents the mean value of deviation.

Figure 3

Bland–Altman plots of sleep stages (n = 49). NREM, light sleep (NREM1 + NREM2), deep sleep (SWS, NREM3) and REM sleep = rapid eye movement sleep (all expressed in minutes). x-axis represents the mean values of the device and PSG; y-axis represents the differences between the PSG and the device; dashed black line represents the upper and lower limit of agreement (mean +/− 1.96 SD); solid red line represents the mean value of difference; solid blue line represents the trend line; shaded green area represents 95% CI (confidence interval) of mean difference.

Figure 4

Boxplot analysis of calculated deviation (a) in sleep stages, Garmin and Polar against the gold standard PSG (n = 49), Light = light sleep, Deep = slow-wave sleep (SWS), REM = rapid eye movement sleep (all expressed in minutes) and (b) in sleep onset time = start of sleep and wake-up time = end of sleep (deviation expressed in minutes), Garmin, Polar and accelerometer (ActiGraph GT9X) against the gold standard PSG (n = 49); the x represents the mean value of deviation.

Figure 5

Night sleep hypnograms (Garmin, PSG, Polar); (a) CPAP patient (male); (b) sleep patient (female). Arousal = partial, temporary or complete wake-up reaction with sleep-disrupting effect [66]; MT = movement time; Wake = awake time; REM = rapid eye movement sleep; S1–S3 represent NREM1–NREM3 (N1 + 2 = light sleep; N3 = deep sleep [70]). x-axis represents the time in hours; y-axis represents the respective sleep stage.