Language Differences Among Individuals with Normal Cognition, Amnestic and Non-Amnestic MCI, and Alzheimer’s Disease

Abstract

Objective: To investigate differences in language performance among older adults with normal cognition (CN), mild cognitive impairment (MCI), and Alzheimer’s disease (ad). Owing to the conflicting literature concerning MCI, discrepancies between amnestic (aMCI) and non-amnestic MCI (naMCI) were explored in greater detail. Method: The study sample was drawn from the older (>64 years) HELIAD cohort. Language performance was assessed via semantic and phonemic fluency, confrontation naming, verbal comprehension, verbal repetition as well as a composite language index. Age, sex, and education adjusted general linear models were used to quantify potential pairwise differences in language performance. Results: The present analysis involved 1607 participants with CN, 146 with aMCI [46 single and 100 multi-domain aMCI], 92 with naMCI [41 single and 51 multi-domain naMCI], and 79 with ad. The mean age and education of our predominantly female (60%) participants were 73.82 (±5.43) and 7.98 (±4.93) years, respectively. MCI individuals performed between those with CN and ad, whereas participants with aMCI performed worse compared to those with naMCI, especially in the semantic fluency and verbal comprehension tasks. Discrepancies between the aMCI and naMCI groups were driven by the exquisitely poor performance of multi-domain aMCI subgroup. Conclusions: Overall, individuals could be hierarchically arranged in a continuum of language impairment with the CN individuals constituting the healthy reference and naMCI, aMCI, ad patients representing gradually declining classes in terms of language performance. Exploration of language performance via separation of single from multi-domain naMCI provided a potential explanation for the conflicting evidence of previous research.