A state of progression in an individual of a disease or treatment having motion symptoms is determined. A time series of accelerometer data is obtained from an accelerometer worn on an extremity of the person, over an extended period during everyday activities of the person. The accelerometer data is processed to produce a plurality of measures of kinetic state of the individual at a respective plurality of times throughout the extended period, each measure of kinetic state comprising at least one of: a measure for bradykinesia, and a measure for dyskinesia. A measure of dispersion of the measures of kinetic state is determined. An output is generated, indicating that motion symptoms are at an initial stage if the measure of dispersion is less than a threshold, or indicating that motion symptoms are at an advanced stage if the measure of dispersion is greater than the threshold.
