Cognitive Performance associated to functional outcomes in stable outpatients with schizophrenia

Prevalence data of cognitive impairment in Schizophrenia based on large population samples are scarce. Our goal is to relate cognition and functional outcomes, and estimate prevalence of cognitive impairment in a large sample of schizophrenia outpatients treated with second-generation antipsychotics.

A cross-sectional outpatient evaluation conducted during follow-up visits. Selection criteria included six-months stable treatment. The brief battery, EPICOG-SCH, covered four cognitive domains related to functional outcomes: working memory (WAIS-III-Letter-Number-Sequencing), executive function (Category Fluency Test; CFT), verbal memory (WMS-III-Logical-Memory), and information processing speed (Digit-Symbol-Coding and CFT). Clinical severity and functional impairment were assessed with CGI-SCH and WHO DAS-S. Impairment prevalence was calculated at ≤ 1.5 SD.

Among patients recruited (n = 848) in 234 participating centers, 672 were under 6-month treatment. 61.5% (n = 413) reported cognitive impairment according to CGI-SCH Cognitive Subscale. Estimated prevalences were 85.9% (95% CI 85.6-86.2%) CFT-Fruits; 68.3% (95% CI 67.8-68.8%) CFT-Animals; 38.1% (95% CI 37.5-38.3%) Digit-Symbol-Coding; 24.8% (95% CI 24.1-25.5%) Verbal Memory-Units; 20.9% (95% CI 20.2-21.6%) Letter-Number Sequencing; 11.7% (95% CI 11.0-12.4%) Verbal Memory-Items. Negative and Depressive symptoms, Deficit Syndrome, and functional disability were related to poor performance. Functional disability was predicted by CGI-SCH-Overall severity (OR = 1.34635, p < 0.0001), CGI-SCH-Negative Symptoms (OR = 0.75540, p < 0.0001), working memory (Letter-Number-Sequencing) (OR = - 0.16442, p = 0.0004) and the time-course (OR = 0.05083, p = 0.0094), explaining 47% of the observed variability.

Most prevalent impairments were on executive function and processing speed domains; however, working memory showed the strongest relationship to functional disability. Monitoring cognitive function during follow up is critical to understand patient's everyday functional capacity.