Abstract: A method to detect drowsiness of an individual. The method includes: (a) acquiring a cardiac signal; (b) processing the cardiac signal to detect time intervals between successive heartbeats; (c) extracting, from the time intervals, characteristic HRV variable(s) of the heart rate variability, each HRV variable being obtained from a plurality of the time intervals; (d) calculating at least one direction aggregate for the HRV variable(s), each being a variable calculated from the HRV variable in a sliding time window, and which characterizes a trend in the window, and/or calculating at least one shape aggregate for the HRV variable(s), each being calculated from values of the HRV variable in a sliding time window and quantifying the shape of a distribution of values of the HRV variable in the window; and (e) processing the direction aggregate(s) and/or the shape aggregate(s) using a detection algorithm enabling detection of drowsiness of the individual.