Defining Alzheimer's disease: stipulations and the ethics of diagnostic change.

Recent revisions of Alzheimer’s Disease (AD) definitions by two leading research groups—the Alzheimer’s Association and the International Working Group—reflect divergent approaches: the former promotes a strictly biological definition, while the latter promotes a clinicalbiological construct. We contend that this emerging controversy is not merely semantic, but scientifically, clinically, and politically significant. Drawing on philosophical tools and situating the current debate within a broader historical context from the reconceptualization of AD in the 1970s onwards, we explore how definitions can serve as transformative instruments, acting as strategic bets that reshape scientific fields and clinical practices. Ultimately, we draw from the AD case study to argue for a critical reflection on the risks and promises of such definitional acts. We also propose a renewed attention to the 'ethics of stipulating' in the field of contemporary biomedical sciences.