Assessing cognition and daily function in early dementia using the cognitive-functional composite: findings from the Catch-Cog study cohort

Abstract

Background: The cognitive-functional composite (CFC) was designed to improve the measurement of clinically relevant changes in predementia and early dementia stages. We have previously demonstrated its good test-retest reliability and feasibility of use. The current study aimed to evaluate several quality aspects of the CFC, including construct validity, clinical relevance, and suitability for the target population. Methods: Baseline data of the Capturing Changes in Cognition study was used: an international, prospective cohort study including participants with subjective cognitive decline (SCD), mild cognitive impairment (MCI), Alzheimer's disease (AD) dementia, and dementia with Lewy bodies (DLB). The CFC comprises seven existing cognitive tests focusing on memory and executive functions (EF) and the informant-based Amsterdam Instrumental Activities of Daily Living Questionnaire (A-IADL-Q). Construct validity and clinical relevance were assessed by (1) confirmatory factor analyses (CFA) using all CFC subtests and (2) linear regression analyses relating the CFC score (independent) to reference measures of disease severity (dependent), correcting for age, sex, and education. To assess the suitability for the target population, we compared score distributions of the CFC to those of traditional tests (Alzheimer's Disease Assessment Scale-Cognitive subscale, Alzheimer's Disease Cooperative Study-Activities of Daily Living scale, and Clinical Dementia Rating scale). Results: A total of 184 participants were included (age 71.8 ± 8.4; 42% female; n = 14 SCD, n = 80 MCI, n = 78 AD, and n = 12 DLB). CFA showed that the hypothesized three-factor model (memory, EF, and IADL) had adequate fit (CFI = .931, RMSEA = .091, SRMR = .06). Moreover, worse CFC performance was associated with more cognitive decline as reported by the informant (β = .61, p < .001), poorer quality of life (β = .51, p < .001), higher caregiver burden (β = − .51, p < .001), more apathy (β = − .36, p < .001), and less cortical volume (β = .34, p = .02). Whilst correlations between the CFC and traditional measures were moderate to strong (ranging from − .65 to .83, all p < .001), histograms showed floor and ceiling effects for the traditional tests as compared to the CFC.

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“…Composite scores are commonly used in cognitive research, as they have less variability than individual neuropsychological test scores, and can reduce floor and ceiling effects. 26 Each model included treatment group (aspirin vs placebo), annual visit/time (0 [baseline], 1, 3, 4, 5, 6), a participantspecific intercept (baseline score), and a participant-specific slope describing change in score over time (per annual visit). To examine whether the trajectory of cognitive scores for an average participant differed between treatment groups, a treatment by time interaction was included in the model.…”

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“…Alzheimer’s disease (AD) is a chronic and progressive disorder causing deterioration of cognitive function beyond the normal aging process among older people worldwide, ranging in severity from predementia stages such as mild cognitive impairment (MCI) to clinical stages of dementia [1]. As a leading chronic disease contributing to disability and dependence, AD is characterized by progressive cognitive decline and growing functional impairment, beginning with mild difficulties with instrumental activities of daily living (ADL), such as using a telephone and managing medication, and ending with the loss of basic ADL, such as bathing, eating, and dressing [2].…”

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

“…The current study results bear crucial implications for AD clinical trials, since the CDR-SB is currently still widely-applied as primary clinical endpoint of efficacy. Previous studies have already indicated limitations of the CDR-SB as outcome measure of change, relating to its poor inter-rater reliability [21] and ceiling effects in scoring in MCI and mild dementia [28]. Our current study findings suggest that the CFC could offer advantages over the use of the CDR-SB as measure to evaluate clinical progression, as it provides a concise and objective measure of clinically meaningful cognitive decline.…”

“…Previous studies on the CFC already demonstrated its good test-retest reliability, feasibility of use, construct validity, and suitability for the target population (i.e. MCI and mild dementia due to AD) [27, 28, 42]. Additionally, separate studies on the cognitive and functional component previously showed their sensitivity to change over time [23, 43].…”

“…Full details on the selected CFC measures have been reported elsewhere [22, 28]. Briefly, the cognitive test battery of the CFC includes the three ADAS-cog memory subscales Word Recognition (score range 0-12), Word Recall (score range 0-10) and Orientation (score range 0-8) [5]; the Controlled Oral Word Association Test (COWAT; letters D-A-T in Dutch and F-A-S in English, 60 seconds) [36]; Category Fluency Test (CFT; animals, 60 seconds) [36]; Digit Span Backward (DSB, score range 0-14) [37] [1] and Digit Symbol Substitution Test (DSST, 90 seconds) [38].…”