Neuropsychological subgroups of dementia of the Alzheimer's type
The present study considered the notion that Neuropsychological subgroups exist within the diagnosis of Dementia of the Alzheimer's Type (DAT). Specifically, the scores on the Cognitive Examination (CAMCOG) of the Cambridge Index of Mental Disorders in the Elderly for 51 DAT patients and 79 normal adults were analyzed via cluster analysis in an attempt to derive meaningful groupings of patients.Results suggested that the CAMCOG was effective in separating normal from impaired individuals. The results also suggested the existence of 4 subgroups within DAT, which were best interpreted as "levels" or "degrees" of impairment. These levels were characterized by distinctly different CAMCOG subscale profiles. Higher performing groups overall showed greatest deficits in memory functions. The most severely impaired group was characterized by dramatically poorer language skills. Mean ages of the DAT groups was similar so that age alone did not appear to contribute to cluster differences. Moreover, information regarding time since onset of symptoms did not suggest that poorer performance was merely a function of the length of time the disease had progressed. A discriminant analysis revealed that the CAMCOG subscales most effective in separating the groups overall were Abstract Thinking, Orientation, Recent Memory, Learning Memory and CAMCOG total score. The CAMCOG appeared to offer some utility in identifying demented patients and in further describing their varied neuropsychological strengths and weaknesses. Implications for using the CAMCOG in planning for care of DAT patients was discussed. Further research is needed to determine other underlying functions contributing to cluster differences and in identifying everyday functional skills of persons with a given CAMCOG profile.