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. / Department of Educational Psychology

In an attempt to characterize the nature of semantic memory impairment in persons with dementia of the Alzheimer type (DAT), a free association task, a definition task, and an associate rank ordering task were administered to 10 mildly and 13 moderately impaired DAT subjects, and 14 normal control subjects. The DAT subjects presented a free association response profile that was markedly different from normal controls. Further, DAT subjects provided meaningful definitions to many of the words used as stimuli in the free association task. Relative to controls, DAT subjects demonstrated a deterioration in their ability to rank order words according to the strength of their association to a stimulus noun. The presently obtained data suggest that the semantic memory impairment in DAT can be characterized, in part, as a deterioration in the associative structure between concepts and a loss of conceptual knowledge.

The purpose of this investigation was to determine the test-retest response consistency rate on a semantic memory task in persons with dementia of the Alzheimer type (DAT). Ten mildly and 13 moderately impaired DAT subjects and 14 normal controls matched for age, years of education, and estimated IQ participated in this study. The Peabody Picture Vocabulary Test (PPVT) was administered twice to each subject with a seven day inter-test interval. The mild and moderate DAT subjects responded inconsistently to significantly more PPVT items than normal controls. When the effects of guessing were considered, moderate DAT subjects gave significantly more inconsistent PPVT responses than normal controls and mild DAT subjects showed a trend towards giving more inconsistent responses. These results substantiate the conclusion that the impairment of specific conceptual knowledge in DAT subjects cannot be reliably measured with a single administration of a semantic memory task such as the PPVT.

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[Truncated abstract] Background: Dementia, largely due to Alzheimer's disease (AD), is a major public health problem. The early identification of disease is an important challenge for clinicians because treatment of AD is now available. A simple and accurate means of stratifying risk for AD and identifying early disease is needed so that risk factor modification and treatment can occur optimally. To date, despite many attempts, an accurate means of standardising an approach to the assessment of subtle cognitive symptoms has not been developed. A subjective complaint of poor memory has been identified as a possible marker for underlying brain disease. This study examines the utility of neuropsychological scores, homocysteine levels, APOE genotyping and brain imaging as predictors of cognitive decline in individuals with subjective memory complaint (SMC). Method Eighty subjects with SMC were recruited from memory clinics and the community (MC: 1). Forty-two control subjects were also examined (MC: 0). CAMDEX was used to describe baseline clinical features. The CAMCOG was used as a global test of cognition and was administered annually for four years. At baseline, neuropsychological testing was administered. Cranial CT scanning, measurement of plasma homocysteine and APOE genotyping were completed. Categorical variables were analysed using chi-square according to Pearson's method. Continuous data was analysed using Student's t-tests and Mann-Whitney tests. A logistic regression model was used to identify independent contributors to the presence of memory complaint. Participants were then matched for age, gender and time to follow-up (up for three years) to determine longitudinal predictors of cognitive decline. ... Baseline CAMCOG scores were greater in the control group (MC:0 = 98.3 ? 2.8, MC:1 94.2 ? 5.5, Z ?4.46, p 0.000). There were no differences in neuropsychological scores, concentration of total plasma homocysteine, APOE genotype or brain scan measurements. Using the Wald stepwise selection method, logistic regression could not be established due to non-convergence regardless of whether or not the continuous variables were re-coded into dichotomous variables. A matching process that created 32 pairs of controls/subjects allowed follow-up analysis. The controls showed significant improvement with time on the CAMCOG unlike subjects (mean ? SD, controls 1.5 ?-3.0, Z - 2.61, p 0.01, subjects 0.2 ? 3.2, Z ? 0.24, p 0.81). The logistic regression analysis showed that group membership could not be defined by any single independent variable. When group membership was abandoned and those with stable scores were compared to those who declined no clear meaningful independent predictors of decline apart from age were identified. Conclusions: Methodological issues such as small sample size and inadequate follow up duration were identified that may have precluded identification of predictive factors for cognitive decline. The results indicate that complaints of memory problems are not associated with established risk factors for Alzheimer's disease and fail to predict objective cognitive decline over three years. Future studies should continue trying to identify robust predictors of cognitive decline in later life.