The present application relates to a system comprising a hearing aid, the hearing aid configured to be operated based on an estimation of a current listening effort of a hearing aid user. The system comprising an input unit for receiving an input sound signal from an environment of the hearing aid user and providing at least one electric input signal representing said input sound signal, an output unit for providing at least one set of stimuli perceivable as sound to the hearing aid user based on processed versions of said at least one electric input signal, a signal-to-noise ratio (SNR) estimator for determining an SNR in the environment of the hearing aid user, a processing unit connected to said input unit and to said output unit and comprising signal processing parameters of the system to provide processed versions of said at least one electric input signal, a memory unit configured to store reference sets of SNR and pulse transition time (PTT) of the hearing aid user, at least a first and a second physiological sensor, wherein the system being configured to determine, based on the first physiological sensor, a first point in time at a first maximum upslope point of a first measured parameter, determine, based on the second physiological sensor, a second point in time at a second maximum upslope point of a second measured parameter, establish a current PTT by calculating a time difference between the first point in time and the second point in time, and determine, based on the current PTT and the stored reference sets of SNR and PTT, a current listening effort of the hearing aid user.