Heterogeneity in the cognitive profile of normal elderly.

An increasing number of studies point to the fact that distinct cognitive subgroups may be identified among subjects with dementia of the Alzheimer type (DAT). Although such heterogeneity could be the expression of neuropsychological, genetic, or epidemiological factors, the identification of neuropsychological subtypes in DAT could also reflect the existence of cognitive subgroups in a normal aged population. In the present study, the existence of neuropsychological subgroups was sought from among 81 volunteers aged between 55 and 84 years. Subjects were given a neuropsychological battery addressing various aspects of cognitive functioning. Results show that six subgroups could be identified among this population. Subgroups differ primarily in their overall degree of performance. Qualitative differences in cognitive performance are also present, mostly when subgroups which exhibit poor overall performance are considered. Consequently, the presence of such heterogeneity in normal elderly should be taken into account in any attempt to identify neuropsychologically based subgroups in early dementia of the Alzheimer type.