The accuracy of the optical heart rate and sleep measurement of two multi-sport activity trackers in a sleep laboratory study

In summary, this study showed high accuracy in measurements of vital data (HR, HRV, SpO2 and respiratory rate) during one night of sleep examination. When measuring the sleep-relevant parameters (TIB, TST, Awake (SOL and WASO) and SE), the multisport activity trackers showed significant differences from the PSG measurement with medium to large effect sizes, with the exception of the TIB measurement. TST was overestimated and awake times underestimated; Garmin deviated significantly more than Polar. The accelerometer ActiGraph GT9X showed significant deviations in the SOL measurement only with medium effect size. In the sleep stage measurement (light, deep, REM sleep), the detection and measurement of time spent in individual sleep stages and states were particularly problematic for both commercial trackers. Again, Garmin deviated more than Polar, with significant differences and medium to large effect sizes by underestimating deep sleep und overestimating light sleep. Neither multisport activity tracker detected or calculated the multiple sleep latency test (MSLT). The accelerometer ActiGraph GT9X confirmed the known accuracies to determine sleep/wake patterns and could be used as a possible reference for further scientific studies under free-living conditions. The use of the multisport activity trackers (Garmin Forerunner 945 and Polar Ignite) for sleep analysis can only be recommended for everyday use and general purposes to give important feedback to active populations and for research purposes where large sample sizes are needed. If precise data on sleep stages and parameters are required, their use is limited. Further studies are needed to evaluate their use for medical purposes, both inside and outside of the sleep laboratory. Follow-up studies are recommended with the newest devices, including elderly sleep patients with sleep disorders and other physical limitations such as obesity BMI status.