ALZHEIMER-DISEASE AND RELATED NEURODEGENERATIVE DISEASES IN ELDERLY PATIENTS WITH SCHIZOPHRENIA - A POSTMORTEM NEUROPATHOLOGIC STUDY OF 100CASES

Background: Clinical studies suggest that severe cognitive impairment is common among elderly patients with schizophrenia who reside in long -stay psychiatric institutions; however, previous autopsy-based neurop athologic investigations have provided conflicting results about the o ccurrence of Alzheimer disease (AD) in elderly patients with schizophr enia. We report the results of a comprehensive neuropathologic study p erformed to identify AD and other dementing neurodegenerative diseases in elderly patients with schizophrenia. Methods: A neuropathologic ex amination was performed on 100 consecutive autopsy brain specimens of patients aged 52 to 101 years (mean, 76.5 years). A cognitive assessme nt of these cases was also done by employing the Clinical Dementia Rat ing Scale. For comparison, we included 47 patients with nonschizophren ic psychiatric disorders from the same psychiatric hospital and 50 age -matched control subjects. Results: Although 72% of the patients with schizophrenia showed cognitive impairment, AD was diagnosed in only 9% of the patients and other dementing diseases were diagnosed in only 4 % of the patients. The degree of senile plaques or neurofibrillary tan gles was not different in the group with schizophrenia compared with t he age-matched controls or the group with nonschizophrenic psychiatric disorders. The higher Clinical Dementia Rating Scale scores lacked co rrelation with neuropathologic evidence of dementing disorders. In the 87 cases lacking a neuropathologic diagnosis of AD or other dementing disorders, the mean (+/-SD) Clinical Dementia Rating Scale score was 2.21 (+/-1.14), with 43 of the cases scoring 3 or higher (indicating s evere, profound, or terminal cognitive impairment). Conclusions: This study provides evidence that elderly patients with schizophrenia are n ot inordinately prone to the development of AD or to increased senile plaques or neurofibrillary tangle formation in the brain. Other dement ing neurodegenerative disorders are also uncommon. The cognitive impai rment in elderly patients with schizophrenia must, therefore, be relat ed to some alternative mechanisms.