Fig. (4) Virtual graph (*) of the possible effects of a symptomatic treatment. *: In reality, the natural evolution of impairment is not lineal and varies according to the stage of the disease; however, the lineal diagram facilitates the conceptual understanding of the action of the drugs. 1: Cognitive decline related to ageing. 2: Cognitive and functional loss due to an untreated progressive disease. 3a: If a symptomatic treatment starts late, the improvement catches that of patients who began treatment earlier. 3b: If the treatment also modifies the course of the disease, its late onset does not allow reaching the benefit obtained with an earlier onset.