Novel peptides and the quantitative methods for the determination thereof in body fluids of patients suffering from progredient chronic dementia, in relation to the concentration of said peptides in a control group. The peptides derive from a protein precursor having the corresponding gene, are processed in a specific manner, and are optionally post-translationally modified, especially phosphorylised. An increase in the concentrations of these peptides or the corresponding non-processed protein indicates progredient chronic dementia. Also disclosed are methods of using the peptides for controlling the course of progredient chronic dementia and for the prognosis of progredient chronic dementia, especially for complementing or replacing mini-mental scores, and for developing therapeutic agents to combat progredient chronic dementia such as Alzheimer's disease.