Vulnerability to Proactive Semantic Interference and Progression to Dementia among Older Adults with Mild Cognitive Impairment

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Abstract
There is evidence that vulnerability to proactive semantic interference may be an early manifestation of early Alzheimer's disease and other neurodegenerative disorders. At present, there is a paucity of data regarding the extent to which such deficits relate to the progression of cognitive deficits and to clinically significant endpoints such as dementia. In this study, we followed 76 older adults, initially diagnosed with mild cognitive impairment, for a period of up to 3 years. Twenty-seven of these individuals (35.5%) progressed from mild cognitive impairment to dementia. An examination of baseline neuropsychological performance indicated lower baseline scores for object memory among those progressing to dementia. However, baseline Mini-Mental State Examination scores, delayed memory for passages, delayed visual memory, letter fluency, category fluency, Trails B and Block Design did not differ among study groups. In contrast, the Semantic Interference Test, a measure susceptible to vulnerability to proactive semantic interference showed the greatest baseline differentiation between those who progressed and those who did not progress to dementia. Further, scores on this measure predicted future progression to dementia with high accuracy. Vulnerability to proactive interference may be an early manifestation of an early dementing process and may have utility in predicting future progression to dementia.