BACKGROUND/AIMS: Current findings suggest the existence of a category of fast cognitive decliners with a poorer prognosis but better treatment response. Our study aimed at confirming the concept of fast decliners at the time of Alzheimer's disease (AD) diagnosis which best predicts mortality, in an unselected sample. METHODS: 245 incident cases of AD were selected from the French longitudinal cohort PAQUID. We investigated a different threshold of cognitive decline [measured by the annual loss of points in the Mini Mental State Examination (MMSE) score] to define when a subject could be considered as a fast decliner. We used Cox proportional hazards models to study the relation between cognitive decline and mortality. RESULTS:The significant threshold of decline associated with a higher mortality rate was a loss of 3 points per year in the MMSE score. Among the 245 AD cases, 83 (33.9%) subjects were considered as fast decliners. Of them, 78.3% died during the follow-up compared with 63.0% of the slow decliners (RR = 1.7, 95% CI 1.2-2.5). CONCLUSION:These results constitute an empirical validation of the concept of fast decliners in community-based AD patients and justify the cutoff of 3 points for the definition of this condition.