According to the commonly accepted model, Alzheimer’s disease is characterized by an ineluctable sequence, from the accumulation of toxic proteins in the brain to dementia resulting from neurodegeneration. While this deterministic sequence is sometimes true, it does not seem to be the case for all patients. Moreover, the disappointing results of recently marketed drugs have highlighted the need to reconsider this disease, which affects nearly 10 million people in Europe. A European consortium of physicians and scientists, led by the University of Geneva (UNIGE) and the University Hospitals of Geneva (HUG), in Switzerland, which also includes INSERM in France, has analyzed the data presented in nearly 200 previously published studies. Far from being a monolithic disease where the same causes produce the same effects, this analysis proposes a categorisation of patients into three groups, each with its own dynamics. In addition, the research team calls for an increased effort to screen people at risk, in order to implement preventive measures as early as possible. This work, to be read in the journal Nature Reviews Neuroscience, proposes a profound paradigm shift in the way Alzheimer’s disease is understood.