Evaluation of the Age Dependence of Conventional and Novel Photoplethysmography Parameters

Background Cardiovascular (CV) mortality increases with age partly due to physiological ageing of the CV system. Early vascular ageing raises CV risks. Personalizing CV risk assessment by defining CV age could reduce CV events. Photoplethysmography (PPG), which analyses the peripheral arterial pulse wave, may be an effective method for estimating CV age. Ageing index (AGEi) and some other PPG parameters were proven to have age correlation; however, the age dependence of many other pulse wave parameters remains unclear. We aimed to identify age correlations of PPG indices and pulse rate variability (PRV) parameters including a few novel parameters which were calculated to further investigate the various aspects of ageing. Our study included 118 healthy (M/F: 53/65, mean age: 31.8 ± 11.8 SD) volunteers for PPG parameter calculation and 106 (M/F: 44/62, mean age: 32.6 ± 12.2 SD) for PRV parameters (age: 19–74). 2-min pulse wave recording was obtained using a pulse oximeter. An automated, proprietary software evaluated PPG and PRV parameter values, which were compared with chronological age (Pearson correlation and non-linear analysis). Results PPG parameters describing various time-dependent aspects of cardiac ejection positively correlated with age, while those indicating arterial elasticity showed negative correlation. Composite PPG parameters proposed as indicators of CV health and fitness had negative, non-linear correlation. Most PRV parameters exhibited negative correlation, indicating reduced adaptive capacity due to ageing ( p < 0.05, IrI > 0.3). Conclusions PPG-based pulse waveform analysis provides a wide range of age-related parameters which display different patterns of age correlation, making it a promising method for estimating cardiovascular age. Future studies will include subjects with vascular ageing conditions beyond physiological values (e.g., hypertension, heart failure, coronary artery disease).