A Comparative Study Between ECG- and PPG-Based Heart Rate Sensors for Heart Rate Variability Measurements: Influence of Body Position, Duration, Sex, and Age

This study evaluated the validity of a photoplethysmography (PPG)-based sensor (Polar OH1) for measuring heart rate variability (HRV), compared to an electrocardiography (ECG)-based reference device (Polar H10), considering body position (supine vs. seated), recording duration (2 vs. 5 min), sex, and age (≤40 vs. >40 years). HRV parameters (RMSSD and SDNN) were analyzed in 31 healthy adults using intraclass correlation coefficients (ICCs) and Bland-Altman analyses. Excellent reliability was observed between the devices in the supine position (RMSSD: ICC = 0.955; SDNN: ICC = 0.980), and good to excellent reliability in the seated position (RMSSD: ICC = 0.834; SDNN: ICC = 0.921). Mean biases ranged from -2.1 ms to -8.1 ms, with wider limits of agreement in the seated condition. The change in posture from supine to seated resulted in moderate reliability for both metrics, regardless of the device. Only marginal differences were found between 2- and 5-min recordings. Moreover, agreement was less consistent in older participants and females, suggesting potential effects of age and sex on signal quality. These findings support the use of PPG-based devices for short-term HRV assessment at rest, while highlighting the importance of considering posture, age, and sex when interpreting the results.