The Role of the Acceleration Plethysmography (APG) Signal for Vascular Aging Analysis With a Modular High-Sampling-Rate Wristband

This study proposes a wearable prototype with a high sampling rate capable of simultaneously acquiring photoplethysmographic (PPG) signals from both the wrist and the finger using red and green wavelengths. By integrating acceleration plethysmography (APG) indices, derived from the second derivative of the PPG signal, the proposed device paves the way for the assessment of arterial stiffness. The proposed approach is motivated by the correlation between vascular aging and the characteristic APG fiducial point indices, as well as their link to the risk of cardiovascular diseases. However, the impact of wavelength and anatomical measurement site on these indices remains largely unexplored in the existing literature. The device was tested on 22 healthy volunteers (mean age 57.8 pm 17.3 years) to assess the correlation between the b/a and e/a indices and chronological age, which was used as a surrogate for vascular age. The results show that the green wavelength provides stronger correlations than red at both sites, and that the finger is the most accurate measurement site (b/a: R = 0.587, p = 0.004; e/a: R = -0.512, and p = 0.015 for green light). At the wrist, only the green wavelength showed trends consistent with physiology and the literature. These preliminary results confirm the validity of the approach and open the way for the integration of APG analysis into wrist-worn devices for cardiovascular screening.