Signal processing
Vascular Age Estimation from PPG
Vascular age estimation from PPG uses the second derivative of the photoplethysmogram (SDPPG/APG) wave ratios and pulse wave morphology features to estimate arterial stiffness, providing a biological age estimate that may differ from chronological age and reflects cardiovascular risk.
How it works
Schematic summary of this guide. Waveforms are illustrative, not measured data.
The acceleration plethysmogram (APG, second derivative of PPG) produces five characteristic waves labeled a through e. Individual wave ratios (b/a for early systolic augmentation, d/a for diastolic reflection) provide additional arterial stiffness markers.
Vascular age is estimated by comparing an individual's AGI or stiffness index to population-based age-specific reference curves. A 40-year-old with the AGI of a typical 55-year-old has a vascular age of 55, indicating premature arterial aging.
These models capture subtle waveform features beyond the five APG waves, including diastolic decay characteristics and beat-to-beat variability in morphology. Consumer implementations are emerging in blood pressure monitoring apps that report vascular health scores derived from smartphone camera PPG.
Frequently Asked Questions
How accurate is PPG-based vascular age?
Individual estimates carry substantial uncertainty, so they are better suited to trend monitoring than precise individual assessment.
Can lifestyle changes improve vascular age from PPG?
Treatments and lifestyle changes that lower arterial stiffness would be expected to shift these markers, but individual PPG vascular-age estimates should be interpreted cautiously.
Is finger or wrist PPG better for vascular age?
Finger PPG provides clearer dicrotic notch and APG waves due to higher perfusion, yielding more reliable vascular age estimates. Wrist PPG can estimate vascular age but with greater measurement variability.