Age-associated photoplethysmographic features across systolic blood pressure strata: a cross-sectional study

Age-related vascular changes may alter photoplethysmographic (PPG) waveform morphology, timing, harmonic composition, and pulse rate variability. However, no evidence confirms that these age-associated PPG characteristics are consistent across different systolic blood pressure (SBP) levels. This cross-sectional study descriptively compared PPG-derived features between adults aged <65 and ≥65 years across four measured SBP strata and evaluated their associations with continuous age using multivariable regression. We included 1,163 cardiology outpatients. Within each stratum, age group differences were evaluated using the Mann–Whitney U test. An exploratory intersection analysis identified 11 candidate PPG-derived features showing nominally significant age-group differences across all four strata. After within-stratum FDR correction across all screened features, 10 of these candidates retained significance across all four strata. Older adults exhibited higher normalized waveform width indices, prolonged systolic timing, higher systolic to diastolic duration ratio, lower H2/H1 and low/high frequency ratios, and greater variability in pulse wave area than younger adults. Participants with SBP ≤120 mmHg also demonstrated these patterns. The findings identify a set of candidate age-associated PPG features consistently observed across the measured SBP spectrum. After adjustment for measured SBP, sex, body mass index, selected cardiometabolic comorbidities, and antihypertensive medication use, these features remained significantly associated with continuous age. Therefore, changes in waveform morphology, pulse timing, harmonic composition, and PRV-derived spectral characteristics may remain age-related. However, further validation remains necessary.