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. Key Points Question: This study investigates the differences in cognition between patients with mild cognitive impairment (MCI) that ultimately progressed, or not, to Alzheimer's disease. Findings: Those who progressed displayed heightened deficits in both semantic memory and cognitive flexibility at baseline compared to stable patients, while both groups exhibited similar levels of general cognition and episodic memory. Importance: This suggests that older people with MCI who experience deficits in both semantic memory (memory of world facts and common knowledge) and episodic memory (memory of personal life events) are at greater risk of progressing towards Alzheimer's disease than those with deficits solely in episodic memory. Next Steps: To refine our understanding of the prognostic value of different semantic tests