Heart rate variability and pulse rate variability agreement in stress regulation: implications for political psychology

Background: Heart rate variability (HRV) provides information about autonomic regulation and has been associated with resilience to stress. However, its assessment using electrocardiography (ECG) can present practical challenges for large studies and recordings outside the laboratory. Pulse rate variability (PRV), derived from photoplethysmography (PPG), and may provide a more accessible alternative. Objective: This study evaluated agreement between ECG-derived HRV and PPG-derived PRV and examined age, body mass index (BMI), and cardiorespiratory fitness as determinants of HRV. Methods: Simultaneous ECG and finger PPG recordings were obtained from 35 healthy adults (20 females and 15 males; mean age 23.1 years; mean BMI 27.5 kg/m²) under standardised resting conditions. Agreement for the standard deviation of normal-to-normal intervals (SDNN) was evaluated using correlation and Bland-Altman analysis. Multiple linear regression assessed age, BMI, and peak oxygen consumption (VO₂peak) as predictors of ECG-derived SDNN. Results: PRV correlated strongly with HRV for SDNN (r = 0.94, p < 0.001). The mean ECG-minus-PPG bias was 3.30 ms, with 95% limits of agreement from -9.48 to 16.08 ms. Age was negatively associated with SDNN (B = -2.14 ms/year, p < 0.001), whereas VO₂peak was positively associated (B = 1.76 ms per ml/kg/min, p = 0.005). BMI was not independently associated after adjustment. The regression model explained 52% of SDNN variance. Conclusion: Resting PRV provides an accessible approximation of HRV for group-level research in healthy young adults. Its use may facilitate wearable-based investigation of autonomic responses in psychological and political settings. Age and fitness should be measured and modelled when interpreting HRV or PRV, while individual-level interchangeability and broader population validity require further study.