Complex discourse production in mild cognitive impairment: Detecting subtle changes

Abstract

Background: Mild cognitive impairment (MCI) is characterised by memory impairment that is greater than would be expected for an individual's age and educational background. Differentiating MCI from normal cognition in ageing is a compelling social, clinical, and scientific concern. Of those with MCI, 50% progress to Alzheimer's dementia within 5 years, while many individuals remain stable or return to normal functioning. Importantly, early identification of MCI has important implications for speech‐language pathology intervention. Aims: The purpose of this study was to investigate whether performance on a complex elicited discourse production task differentiated individuals with MCI from those with normal cognition. The variables of interest were discourse length, complexity, and quality. Methods & Procedures: Eight individuals with MCI and eight age‐ and gender‐matched controls were tested with the Mini‐Mental State Exam (MMSE), Logical Memory Subtest (LMS) of the Weschsler Memory Scale, and the Boston Naming Test (BNT). For the experimental task, each participant provided a complex, elicited discourse sample that was unconstrained in terms of discourse genre, in response to verbal instructions. Outcomes & Results: The MMSE and LMS scores differentiated the groups in the expected direction, with the control group outperforming the MCI group. The groups performed comparably on the BNT. Performance on the experimental discourse production task distinguished the groups on measures of length and quality, but not in syntactic complexity. Conclusions: These findings suggest that performance on a complex elicited discourse production task uncovers subtle differences in the abilities of individuals with MCI, such that measures of length and quality differentiated them from individuals with normal cognition.