This study conducted to investigate and study the effect of aging on Photoplethysmogram (PPG) signal and the effects of aging on the calculations of reflection index (RI). The results showed that PPG is highly affected by aging which noteworthy to be observed by the variations of PPG contour. Since we advance in age, PPG becomes more rounded which in turn make PPG inflection point and dicrotic notch less pronounced. As a conclusion, RI may provide a window to small and medium arteries compliance and it can be a measure of small and medium arteries stiffness. When small and medium arteries start stiffening, early detection of atherosclerosis in sub-clinical settings can be investigated and detected.