Neuropsychological heterogeneity in mild Alzheimer's disease.

In order to investigate neuropsychological differences in patients with mild AD, we carried out a pilot study on 28 patients with a clinical diagnosis of mild dementia (CDR: 0.5-1) using an extensive neuropsychological battery, in comparison with 28 normal controls. The results of a cluster analysis, applied on the neuropsychological variables, showed the existence of at least two main subgroups of patients. Cluster 1 patients had a mean age of 61.1 years and showed a greater impairment on measures of language, abstract reasoning and verbal fluency; cluster 2 patients, with a mean age of 72.0, had more severe impairment in memory function. These preliminary results may suggest the existence of different subtypes of AD characterized by selective neuropsychological deterioration in the early stages of the disease.