title: Aging Index using Photoplethysmography for a Healthcare Device: Comparison with Brachial-Ankle Pulse Wave Velocity.
abstract: OBJECTIVE
  Recent studies have emphasized the potential information embedded in peripheral fingertip photoplethysmogram (PPG) signals for the assessment of arterial wall stiffening during aging. For the discrimination of arterial stiffness with age, the brachial-ankle pulse wave velocity (baPWV) has been widely used in clinical applications. The second derivative of the PPG (acceleration photoplethysmogram [APG]) has been reported to correlate with the presence of atherosclerotic disorders. In this study, we investigated the association among age, the baPWV, and the APG and found a new aging index reflecting arterial stiffness for a healthcare device.
  
  
  METHODS
  The APG and the baPWV were simultaneously applied to assess the accuracy of the APG in measuring arterial stiffness in association with age. A preamplifier and motion artifact removal algorithm were newly developed to obtain a high quality PPG signal. In total, 168 subjects with a mean ± SD age of 58.1 ± 12.6 years were followed for two months to obtain a set of complete data using baPWV and APG analysis.
  
  
  RESULTS
  The baPWV and the B ratio of the APG indices were correlated significantly with age (r = 0.6685, p < 0.0001 and r = -0.4025, p < 0.0001, respectively). A regression analysis revealed that the c and d peaks were independent of age (r = -0.3553, p < 0.0001 and r = -0.3191, p < 0.0001, respectively).
  
  
  CONCLUSIONS
  We determined the B ratio, which represents an improved aging index and suggest that the APG may provide qualitatively similar information for arterial stiffness.
authors.affiliation: Division of Cardiology, Department of Internal Medicine, Hallym University College of Medicine, Chuncheon, Korea.
authors.forename: Kyung Soon
authors.initials: KS
authors.lastname: Hong
authors.affiliation: Division of Cardiology, Department of Internal Medicine, Hallym University College of Medicine, Chuncheon, Korea.
authors.forename: Kyu Tae
authors.initials: KT
authors.lastname: Park
authors.affiliation: Department of Electronics Engineering, College of Information and Electronics Engineering, Hallym University, Chuncheon, Korea.
authors.forename: Jae Mok
authors.initials: JM
authors.lastname: Ahn
keywords: Acceleration Plethysmogram; Arterial Stiffness; Motion Artifact; Photoplethysmography; Pulse Wave Velocity