The course of functional decline in geriatric patients with schizophrenia: cognitive-functional and clinical symptoms as determinants of change.

OBJECTIVE: Authors sought to use a cognitive assessment instrument validated for assessing low-functioning patients to broaden knowledge about the rate and correlates of functional decline.
METHODS: Patients were examined across a wide range of baseline cognitive and functional status, and changes in cognitive and functional status were examined. A group of 424 elderly patients with schizophrenia were followed up over a 6-year period; 280 of these manifested severe cognitive impairment at baseline. Patients were examined with an instrument designed for cognitive and functional assessment of severe cognitive impairment: the Alzheimer's Disease Assessment Scale-Late (ADAS-L).
RESULTS: Patients with higher and lower baseline scores manifested equivalent declines in the ADAS-L cognitive subscale, but differences in decline on basic activities of daily living. Random-effects regression analysis indicated that functional changes were significantly correlated with cognitive changes for the sample as whole and that cognitive changes were the best predictor of changes in functional status over time. Baseline cognitive status was not a statistically significant covariate for functional change, nor was the course of negative symptoms over the follow-up period.
CONCLUSIONS: Cognitive change appears very similar in magnitude across older, poor-outcome patients with different baselines of cognitive impairment. In contrast, functional decline was limited to patients with lower levels of functioning at baseline. These findings suggest that cognitive thresholds for impairments in different aspects of functional status may exist in patients with schizophrenia. Basic activities of daily living decline only in patients with very low levels of baseline cognitive functioning.