Performance of three consumer sleep-tracking devices compared with Actigraphy and Polysomnography

Area of Science:

• Sleep Science and Technology
• Biomedical Engineering
• Wearable Technology

Background:

• Consumer wearables are increasingly used for sleep monitoring.
• Accurate sleep stage assessment is crucial for diagnosing sleep disorders.
• Validation against gold-standard methods like polysomnography (PSG) is necessary.

Purpose of the Study:

• To evaluate the performance of Apple Watch Series 7, Fitbit Charge 5, and Polar Vantage M2.
• To compare wearable accuracy against home polysomnography (PSG) and actigraphy.
• To assess sleep metrics including time in bed, total sleep time, and sleep stage durations.

Main Methods:

• Prospective observational study on 54 healthy adults (18-45 years).
• Concurrent wear of one consumer wearable, research-grade actigraphy, and home PSG for 7 days.
• Analysis of agreement using intraclass correlation coefficients (ICCs) and Bland-Altman plots.

Main Results:

• Wearables exhibited weak agreement and wide limits of agreement with PSG.
• Fitbit overestimated light sleep; Apple Watch underestimated light sleep and overestimated REM sleep.
• Polar showed a positive bias for REM sleep; Apple Watch ranked highest, followed by Fitbit and Polar.

Conclusions:

• Apple Watch, Fitbit, and Polar demonstrate parameter-specific biases and limited agreement with PSG.
• These consumer wearables are not suitable for clinical-grade sleep architecture assessment.
• They may be appropriate for longitudinal self-monitoring of general sleep patterns.