A system comprising: - a device intended to be attached to the body of an individual, the device comprising measuring means incorporating at least one sensor of the photoplethysmographic type intended to acquire instantaneous raw data; - a first unit for calculating an instantaneous pulse wave value from the instantaneous raw data of the photoplethysmographic sensor; - a storage unit for the calculated pulse wave values; - a processing unit for the stored pulse wave values, comprising: - means for identifying a period for the stored pulse wave values; - a second calculation unit to calculate, for each identified period: - a difference in amplitude and a difference in time between a first point corresponding to a systolic peak and a second point corresponding to a diastolic peak, - a median moment between the first and second points, - a third calculation unit for calculating, from the amplitude differrence, the time difference and the median time, by means of a multivariate statistical analysis, step by step with peripheral calibration, the following three physiological parameters: - an arterial stiffness index; - blood pressure; - a central pressure, - a fourth unit for calculating a time variation value of said three physiological parameters at two different times T. - a device intended to be attached to the body of an individual, the device comprising measuring means incorporating at least one sensor of the photoplethysmographic type intended to acquire instantaneous raw data; - a first unit for calculating an instantaneous pulse wave value from the instantaneous raw data of the photoplethysmographic sensor; - a storage unit for the calculated pulse wave values; - a processing unit for the stored pulse wave values, comprising: - means for identifying a period for the stored pulse wave values; - a second calculation unit to calculate, for each identified period: - a difference in amplitude and a difference in time between a first point corresponding to a systolic peak and a second point corresponding to a diastolic peak, - a median moment between the first and second points, - means for identifying a period for the stored pulse wave values; - a second calculation unit to calculate, for each identified period: - a difference in amplitude and a difference in time between a first point corresponding to a systolic peak and a second point corresponding to a diastolic peak, - a median moment between the first and second points, - a difference in amplitude and a difference in time between a first point corresponding to a systolic peak and a second point corresponding to a diastolic peak, - a median moment between the first and second points, - a third calculation unit for calculating, from the amplitude differrence, the time difference and the median time, by means of a multivariate statistical analysis, step by step with peripheral calibration, the following three physiological parameters: - an arterial stiffness index; - blood pressure; - a central pressure, - an arterial stiffness index; - blood pressure; - a central pressure, - a fourth unit for calculating a time variation value of said three physiological parameters at two different times T.