The Cognitive‐Functional Composite is sensitive to clinical progression in early dementia: Longitudinal findings from the Catch‐Cog study cohort

INTRODUCTION: In an attempt to capture clinically meaningful cognitive decline in early dementia, we developed the Cognitive‐Functional Composite (CFC). We investigated the CFC's sensitivity to decline in comparison to traditional clinical endpoints. METHODS: This longitudinal construct validation study included 148 participants with subjective cognitive decline, mild cognitive impairment, or mild dementia. The CFC and traditional tests were administered at baseline, 3, 6, and 12 months. Sensitivity to change was investigated using linear mixed models and r (2) effect sizes. RESULTS: CFC scores declined over time (β = −.16, P < .001), with steepest decline observed in mild Alzheimer's dementia (β = −.25, P < .001). The CFC showed medium‐to‐large effect sizes at succeeding follow‐up points (r (2 )= .08‐.42), exhibiting greater change than the Clinical Dementia Rating scale (r (2 )= .02‐.12). Moreover, change on the CFC was significantly associated with informant reports of cognitive decline (β = .38, P < .001). DISCUSSION: By showing sensitivity to decline, the CFC could enhance the monitoring of disease progression in dementia research and clinical practice.