PPG-Based Heart Rate Accuracy in Diverse Populations: Investigating Inequities Across Body Composition and Skin Tones

TL;DR

This study assesses the accuracy of popular wrist-worn heart rate monitors across diverse populations, revealing biases linked to body composition and skin tone, and highlighting the need for more equitable health monitoring algorithms.

Contribution

It provides empirical evidence of disparities in wearable HR monitor accuracy across different body types and skin tones, emphasizing the importance of algorithm improvements for equity.

Findings

Apple and Garmin had the lowest error rates.

Higher BMI and darker skin tones increased measurement error.

All devices showed significant deviation from ECG reference.

Abstract

Wearable devices are widely used for heart rate (HR) monitoring, yet their accuracy across diverse body compositions and skin tones remains uncertain. This study evaluated four wrist worn devices (Apple, Fitbit, Samsung, Garmin) in 58 Hispanic adults with Fitzpatrick skin types III to V during a cycling protocol alternating moderate (0.64 to 0.76 HRmax) and vigorous (0.77 to 0.95 HRmax) intensities. Criterion HR was obtained using a Polar H10 ECG, and accuracy was assessed using mean absolute error, mean absolute percentage error (MAPE), bias, and intraclass correlation coefficients. All devices showed significant deviation from criterion measures. Apple and Garmin demonstrated the lowest error, whereas Fitbit and Samsung exhibited greater inaccuracies. Higher BMI and darker skin tones were associated with increased MAPE. These biases disproportionately affect higher risk populations, underscoring the need for improved algorithms to ensure equitable health monitoring.