Methods and apparatus for assessing vascular health

A method for simultaneous assessment of microvascular function and macrovascular function using a skin temperature sensor and a photoplethysmography (PPG) sensor, comprising:

• (a) creating a temporary arterial occlusion;
• (b) measuring skin temperature and PPG signals before, during, and after the arterial occlusion;
• (c) calculating Zero Reactivity Curve (ZRC) based on variables including baseline skin temperature decline during the arterial occlusion according to below formula:
• ZRC[t]=(StartTemp)+(Mintemp−RightStartTemp)*(exp(−1*c*((37−RoomTemp)/(37−RightStartTemp))*t))
• wherein c=−dfdt/(StartTemp−RoomTemp), wherein StartTemp is baseline temperature of a right finger where the occlusion happens, Mintemp is minimum temperature of the right finger after occlusion, RoomTemp is room temperature, and t is time in seconds after minimum temperature of the right finger after occlusion;
• (d) calculating peak-to-base amplitude, peak-to-trough amplitude, pulse waveform analysis, area under the curve analysis, reflectance waveform analysis, or a combination thereof from the PPG signals;
• (e) assessing microvascular function based on comparing observed temperature rebound after the occlusion and the ZRC;
• and
• (f) accessing macrovascular function based on comparing peak-to-base amplitude, peak-to-trough amplitude, pulse waveform analysis, area under the curve analysis, reflectance waveform analysis, or a combination thereof from the PPG signals, before and after the arterial occlusion.