Performance of chronic schizophrenic patients on cognitive neuropsychological measures sensitive to dementia

Although many chronic schizophrenic patients manifest substantial global cognitive impairment, it is not clear as to whether this impairment should be characterized as dementia. Since many degenerative dementias have a characteristic signature of cognitive impairment and a specific pattern of cognitive decline, examination of schizophrenic patients on these measures can provide information about the qualitative similarity of their cognitive impairment to these other conditions. Three hundred and two chronically hospitalized schizophrenic patients ranging in age from 26 to 98 were examined with the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) neuropsychological battery, as well as a more global measure of cognitive impairment, the Mini-Mental State Examination (MMSE). This assessment was repeated twice, with a 1-year follow-up interval. The CERAD battery measures the prototypical cognitive deficits of Alzheimer's disease, including word list learning and delayed recall, naming and praxis. In contrast to Alzheimer's disease, all aspects of cognitive impairment were linearly associated with MMSE scores and there were no qualitatively different patterns of deficits associated with MMSE scores in different ranges of severity. There was no change in performance on any measure across the follow-up period, regardless of the MMSE scores of the patients at baseline. These data suggest that the specific patterns of deficit in chronic schizophrenic patients with severe cognitive deficits differ from Alzheimer's disease in both course and profile of impairment.