Six-year follow-up study of cognitive and functional status across the lifespan in schizophrenia: a comparison with Alzheimer's disease and normal aging.

OBJECTIVE: Follow-up studies of cognitive functions of poor-outcome (long-term institutionalized) elderly patients with schizophrenia have demonstrated deterioration over time, while stable cognitive functions over time have been reported for younger, better-outcome schizophrenic patients. This study examined whether cognitive changes in elderly schizophrenic patients with a history of long-term institutional stay extended to institutionalized younger patients. The rate of decline was compared to changes associated with Alzheimer's disease.
METHOD: Patients with schizophrenia (N=107) age 20-80 years were followed over 6 years and assessed with the Clinical Dementia Rating and the Mini-Mental State Examination. The schizophrenic subjects age 50 and older were compared to 136 healthy comparison subjects and 118 Alzheimer's disease patients age 50 and older who were assessed over a similar follow-up period.
RESULTS: There was a significant age group effect on the magnitude of cognitive decline for the schizophrenic subjects, with older subjects experiencing greater levels of decline over the follow-up. Neither the healthy individuals nor the Alzheimer's disease patients demonstrated similar age-related differences in the magnitude of cognitive change over the follow-up, with healthy comparison subjects showing no change and Alzheimer's disease patients manifesting decline regardless of age at the initiation of the follow-up.
CONCLUSIONS: Institutionalized schizophrenic patients demonstrated an age-related pattern of cognitive change different from that observed for Alzheimer's disease patients and healthy individuals. The cognitive and functional status of these schizophrenic patients was fairly stable until late life, suggesting that cognitive change may not be occurring in younger patients over an interval as long as 6 years.