The Self-Fulfilling Prophecy of Episodic Memory Impairment in Mild Cognitive Impairment: Do Episodic Memory Deficits Identified at Classification Remain Evident When Later Examined with Different Memory Tests?
Previous studies of mild cognitive impairment (MCI) have been criticised for using the same battery of neuropsychological tests during classification and longitudinal followup. The key concern is that there is a potential circularity when the same tests are used to identify MCI and then subsequently monitor change in function over time. The aim of the present study was to examine the evidence of this potential circularity problem. The present study assessed the memory function of 72 MCI participants and 50 healthy controls using an alternate battery of visual and verbal episodic memory tests 9 months following initial comprehensive screening assessment and MCI classification. Individuals who were classified as multiple-domain amnestic MCI (a-MCI+) at screening show a significantly reduced performance in visual and verbal memory function at followup using a completely different battery of valid and reliable tests. Consistent with their initial classification, those identified as nonamnestic MCI (na-MCI) or control at screening demonstrated the highest performance across the memory tasks. The results of the present study indicate that persistent memory deficits remain evident in amnestic MCI subgroups using alternate memory tests, suggesting that the concerns regarding potential circularity of logic may be overstated in MCI research. 1. Introduction The concept of Mild Cognitive Impairment (MCI) emerged from a series of MAYO clinic epidemiological studies attempting to identify predictive risk factors for Alzheimer’s dementia (AD) [1–3]. The utility of MCI was perceived to be its ability to identify individuals most at risk of future cognitive decline, particularly those likely to transition to AD [2]. Subsequently, the clinical features used to classify MCI have gradually been replaced by MCI diagnostic criteria [4, 5], although a number of researchers question whether these criteria lack appropriate sensitivity and specificity to be considered diagnostic [6–12]. Current MCI classification criteria include concern regarding a change in cognitive functioning; evidence of objective dysfunction (usually from neuropsychological assessment); relatively intact daily functioning; and an absence of dementia [4]. According to the diagnostic criteria outlined by Winblad et al. [5], amnestic subtypes are defined by the presence of an episodic memory deficit, whereas non-amnestic subtypes are defined by the presence of a non-memory deficit (e.g., attention, language, working memory). Both of these broad variants may be further classified as single domain (deficits
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