FIELD : medicine.SUBSTANCE : group of inventions relates to medicine. Sleep monitoring method for measuring a biophysical variable of a living being is performed using a device. Sleep monitoring device comprises pressure sensors spatially arranged in a predefined planar geometry and adapted for contacting with a support layer to support a living being during sleep and generating corresponding sensor signals in response to the pressure exerted by a living being through the support layer on the sensors. Processing unit of the sleep monitoring device is adapted to perform the localisation function and the determination function. Localisation function is configured to determine the position of the living being on the support layer relative to the sensors based on the differences between the corresponding sensor signals by performing a measurement procedure based on the phase difference between the respective sensor signals or by performing a measurement procedure based on the difference of magnitude between the corresponding sensor signals. Determination function is configured to determine the magnitude attenuation factor based on the determined position of the living being and the position of one of the sensors and determine the biophysical variable based on the sensor signal and the magnitude attenuation factor.EFFECT : sleep monitoring is achieved with more accurate measurement of the patient’s sleep-related biophysical variables, regardless of the patient’s position on the bed.13 cl, 12 dwg