Capturing functional change in early Alzheimer’s disease: Comparing instruments and scoring techniques to detect subtle decline

Abstract

AbstractBackgroundFunctional decline is a gradual process occurring along the Alzheimer’s disease (AD) continuum, starting years before dementia onset. Different instruments, such as the ADCS‐ADL and the Amsterdam Instrumental Activities of Daily Living Questionnaire (A‐IADL‐Q) aim to capture early functional changes. In the current study, we compared measurement instruments and scoring techniques to find the optimal measurement technique for detecting functional impairment in early AD.MethodStudy partners of participants from the international ‘Capturing Changes in Cognition’ study cohort completed both the A‐IADL‐Q and ADCS‐ADL over the course of one year (mean follow‐up 10.8±2.3 months). For both measures, we computed the following scores: (1) sum score, (2) weighted average, and (3) number of items with maximum score. For the A‐IADL‐Q, we also computed item response theory (IRT) scores, using predetermined parameters that take into account varying difficulty of included items (see Jutten et al., 2017). To compare the ability to detect changes over time for each scoring method, we performed linear mixed modeling, adjusted for sex and baseline age.ResultWe included 159 individuals (72.2±8.4 years old, 45% female) with subjective cognitive decline (SCD, N=12), mild cognitive impairment (MCI, N=66) or mild dementia (N=81). Overall, a significant decline in functioning was detected with all scoring techniques (all p<.01), except the technique of the number of items with most impairment for the ADCS‐ADL (see Table 1). When comparing decline in the diagnostic groups (see Figure 1 and Table 1), linear mixed models showed functional decline in all scoring techniques of both instruments in mild dementia. In MCI, all A‐IADL‐Q scoring methods showed a significant decline over time (p<.05), whereas the ADCS‐ADL scores did not. No decline was detected in SCD.ConclusionThe A‐IADL‐Q showed greater sensitivity to functional decline over one year than the ADCS‐ADL in those with MCI. Our findings suggest that the ability to detect subtle functional changes appears to be mostly dependent on instrument, and to a lesser extent on the scoring technique used. These findings imply that the selection of appropriate instruments is pivotal for optimal longitudinal study design, and clinical trial design in patients with MCI.