System and method for evaluating a variation of a heart rate of a subject

A system for evaluating a variation of a heart rate of a subject, comprising:

• a photoplethysmography signal providing unit for providing a photoplethysmography signal indicative of a heartbeat of the subject;
• a motion signal providing unit for providing a motion signal indicative of a motion of the subject;
• a signal feature determination unit for determining a signal feature of the photoplethysmography signal, wherein the signal feature comprises at least one of an interbeat interval and a morphology of the photoplethysmography signal;
• a motion determination unit for determining a motion period during which motion identifiable in the motion signal corresponds to one of a plurality of predefined motion classes;
• a signal reliability determination unit for determining a signal reliability of the photoplethysmography signal depending on whether a period of the photoplethysmography signal is within or outside a motion influence period, wherein the motion influence period comprises the motion period and a transition period following the motion period;
• and
• a heart rate variation determination unit for determining the variation of the heart rate of the subject based on the signal reliability and on the signal feature of thephotoplethysmography signal.