An Examination of Semantic Performance in Mild Cognitive Impairment Progressors and Nonprogressors

Objective: Mild cognitive impairment (MCI) is a risk factor for developing Alzheimer's disease (AD), and about half of older people with MCI will progress to AD within the next 5 years. The aim of the present study was to compare the semantic performance of MCI progressors (MCI-p) and nonprogressors (MCI-np). The hypothesis was that MCI-p would present with poorer semantic performance relative to MCI-np at baseline, indicating that semantic deficits may increase the risk of future decline toward AD. Method: Fifty-six MCI participants (aged 65-89) from the Consortium for Early Identification of Alzheimer's Disease-Quebec study were analyzed, with 18 progressing and 38 remaining stable over 2 years. Analysis of covariance assessed their initial semantic and nonsemantic cognitive performance, and mixed analyses of variance gauged longitudinal patterns of cognitive decline at the 2-year follow-up. Results: In the semantic domain, MCI-p performed significantly worse than MCI-np at baseline on two semantic tests (category fluency and object decision). In other cognitive domains, MCI-p performed worse than MCI-np on a test of executive functions (cognitive flexibility) but showed similar performance on a test of episodic memory. There were no significant differences between groups in the rates of progression on semantic tests over the 2-year period, but a steeper decline was observed in MCI-p at follow-up on tests of global cognition, episodic memory, and processing speed. Conclusion: This suggest that MCI patients who present with semantic memory impairment in addition to episodic memory impairment are at greater risk of future progression to AD.