Characteristics of beat-to-beat photoplethysmography waveform indexes in subjects with metabolic syndrome

Metabolic syndrome (MetS) increases the risk of the subsequent development of cardiovascular disease. This study aimed to determine if the harmonic indexes of finger photoplethysmography (PPG) waveforms can be used to discriminate different arterial pulse transmission conditions between MetS and healthy subjects. Three-minute PPG signals were obtained in 65 subjects, who were assigned to 3 age-matched groups (MS, with no less than three MetS factors; pre-MS, with one or two MetS factors; Control: with no MetS factor). FDT (foot delay time) and amplitude proportions (Cn) and their standard deviations (SDn) and coefficients of variations (CVn) were calculated for harmonics 1 to 10 of the PPG waveform. FDT was smaller in MS than in Control. C1 and C2 values were significantly smaller, whereas C4-C9 values were significantly or appeared to be larger in MS than in pre-MS. Most of the SDn and CVn values were largest in MS. This study is the first to demonstrate that harmonic-analysis indexes of the beat-to-beat PPG waveform can provide information about MetS-induced changes in the arterial pulse transmission and cardiovascular regulatory activities. The present findings may therefore be useful in developing a noninvasive and easy-to-perform technique that could improve the early detection of cardiovascular diseases.