Estimating Heart Rate from Inertial Sensors Embedded in Smart Eyewear: A Validation Study

Area of Science:

• Biomedical Engineering
• Wearable Technology
• Physiological Monitoring

Background:

• Continuous heart rate (HR) monitoring is crucial for health assessment.
• Smart glasses offer a novel, unobtrusive method for physiological data collection.
• Validation of HR estimation from smart glasses is needed for sedentary activities.

Purpose of the Study:

• To validate the accuracy of heart rate (HR) estimation using Essilor Connected Glasses (SmartEW).
• To assess the performance of SmartEW against ECG and a commercial smartwatch during static tasks.
• To determine the impact of the SmartEW quality index (QI) on HR estimation accuracy.

Main Methods:

• Thirty participants performed six static tasks under controlled laboratory conditions.
• HR was simultaneously measured using SmartEW, a Garmin Venu 3 smartwatch, and a Movesense Flash ECG device.
• SmartEW utilized IMU sensor data and spectral analysis (22.5s windows) for HR estimation and generated a quality index (QI).

Main Results:

• SmartEW demonstrated high agreement with ECG, with optimal performance at a QI threshold of 70.
• At QI ≥ 70, correlation (r² up to 0.96) and accuracy within ±5 bpm (95%) were high.
• A QI ≥ 70 reduced bias and narrowed limits of agreement compared to ECG, especially during standing tasks.

Conclusions:

• Essilor Connected Glasses (SmartEW) provide promising heart rate (HR) accuracy during sedentary activities.
• SmartEW shows high correlation and strong agreement with gold-standard ECG and commercial smartwatches.
• SmartEW is suitable for HR monitoring in static conditions, contingent on ensuring data quality via the QI.