Study partner‐reported decline identifies cognitive decline and dementia risk

OBJECTIVE: Identifying individuals at risk for cognitive decline, Mild Cognitive Impairment (MCI), and dementia due to Alzheimer’s disease (AD) is a critical need. Functional decline is associated with risk and can be efficiently assessed by participants and study partners (SPs). We tested the hypothesis that SP‐reported functional decline is an independent predictor of dementia risk and cognitive decline. METHODS: In 1048 older adults in the Alzheimer’s Disease Neuroimaging Initiative (ADNI), we measured associations between Everyday Cognition Scale scores (ECog, self‐ and SP‐reported versions) and (1) baseline and longitudinal change in neuropsychological test (NPT scores) across multiple cognitive domains; (2) diagnostic conversion to MCI or dementia. Models included Mini Mental Status Exam (MMSE) score and ApoE ε4 genotype (APOE) as predictors. Model fits were compared with and without predictors of interest included. RESULTS: SP‐reported ECog was the strongest predictor of cognitive decline across multiple domains, as well as diagnostic conversion. Self‐reported ECog was associated with baseline NPT scores in some cognitive domains, and diagnostic conversion to MCI in participants with biomarker evidence for AD (elevated brain β‐amyloid, Aβ). Models including SP‐reported ECog were significantly stronger at predicting outcomes. CONCLUSIONS: SP‐reported functional decline is an independent indicator of cognitive decline and dementia risk, even when accounting for cognitive screening, genetic risk, demographics, and self‐report decline. The results provide a rationale for greater utilization of SP‐reported functional decline to identify those at risk for dementia due to AD and other causes.