Clinical stages of normal aging and Alzheimer's disease: The GDS staging system
Phenomenologic, cross-sectional and longitudinal studies have resulted in the identification of characteristic stages of normal aging and progressive Alzheimer's disease (AD). A staging system resulting from these studies is known as the 'GDS Staging System.' Three optimally concordant and potentially independent clinical rating instruments are incorporated in this staging system, the Global Deterioration Scale (GDS), the Brief Cognitive Rating Scale (BCRS) and the Functional Assessment Staging measure (FAST). Definitions of each of the elements of this staging system as well as reliability and concurrent validity data have been published. Clear advantages of the GDS Staging System over other available staging measures include: (1) readily interpretable and clinically meaningful stages and substages; (2) improved definition of the boundaries of normal aging and incipient AD, and (3) the ability to chart the course of the severely impaired, conventionally 'untestable,' portion of AD. Widespread usage of this staging system can potentially advance current research and clinical understanding of normal brain aging and the nature, course and treatment of AD and related conditions.