The stage specific temporal course of Alzheimer's disease: functional and behavioral concomitants based upon cross-sectional and longitudinal observation.

A series of studies published over the past 6 years now permit a relatively precise description of the temporal course of Alzheimer's disease (AD). Initially, 7 global stages of CNS aging and AD were described. Subsequently, data on the stage specific relationship between these stages and widely employed mental status, psychometric, and other assessment measures were collected. Longitudinal studies helped to clarify the borders between normal CNS aging and AD using these measures. Other studies described functioning and self-care correlates of the 7 global stages. These were ultimately divisible into 16 clearly defined, ordinal functional stages. Empirical longitudinal observations permitted the description of the mean temporal course of each of the 16 functional stages of aging and AD. The cross-sectional stage specific data on mental status and other measures can now be applied to the mean temporal course observations and the validity of the temporal estimates forwarded can be investigated in detail. Etiologic hypotheses based upon the observed phenomenologic and temporal course of AD are discussed.