Cognitive Decline in Advanced Age: Future Directions for the Psychometric Differentiation of Normal and Pathological Age Changes in Cognitive Function

In the effort to delineate the cognitive changes that are associated with advanced age, it is necessary to discriminate not only between the cognitive abilities of the young and the aged, but also between the cognitive abilities of the demented and nondemented elderly. The identification of the qualitative characteristics of age-dependent cognitive decline is made difficult by the obscurity of the latter distinction, which is in turn a consequence of the insidious nature of the dementing process (American Psychiatric Association, 1980). It is not particularly helpful to compare the cognitive profile of the normal elderly person with that of the more severely demented patient, because the global nature of the cognitive deterioration in the more advanced stages of senile dementia produces deficits on virtually any cognitive measure, and therefore adds little contrast to the qualitative description of age-specific changes in cognitive function. The approach adopted in the present review was to examine the cognitive losses associated with normal aging and with the early stages of senile dementia of the Alzheimer type in order to identify the changes in cognitive function that are age-dependent, dementia-dependent, neither, or both (see Table 1).