Semantic network function captured by word frequency in nondemented APOE ε4 carriers.

Abstract

Accurate identification of the earliest cognitive changes associated with Alzheimer’s disease (AD) is critically needed. Item-level information within tests of category fluency, such as lexical frequency, harbors valuable information about the integrity of semantic networks affected early in AD. To determine the potential of lexical frequency as a cognitive marker of AD risk, we investigated whether lexical frequency of animal fluency output differentiated APOE ε4 carriers from non-carriers in a cross-sectional design among older African American adults without dementia. We analyzed animal fluency performance using mean number of items and mean lexical frequency among 230 cognitively normal African Americans with and without the APOE ε4 allele. RESULTS: Lexical frequency was higher in APOE ε4 carriers than non-carriers when analyzed as a mean score and within time bins. In contrast, we found no group difference in the number of items produced. Lexical frequency was particularly sensitive to ε4-status after the first 10 seconds of the 60-second animal fluency task. Our results suggest that psycholinguistic features may hold value as a cognitive biomarker for identifying people at high risk of AD.