Abstract
Subjective cognitive decline (SCD) may be an at-risk stage of Alzheimer's disease (AD) occurring prior to amnestic mild cognitive impairment (aMCI). To examine white matter (WM) defects in SCD, diffusion images from 27 SCD (age=65.3±8.0), 35 aMCI (age=69.2±8.6) and 25 AD patients (age=68.3±9.4) and 37 normal controls (NC) (age=65.1±6.8) were compared using Tract-Based Spatial Statistics (TBSS). WM impairments common to the three patient groups were extracted, and fractional anisotropy (FA) values were averaged in each group. As compared to NC subjects, SCD patients displayed widespread WM alterations represented by decreased FA (p<0.05), increased mean diffusivity (MD; p<0.05), and increased radial diffusivity (RD; p<0.05). In addition, localized WM alterations showed increased axial diffusivity (AxD; p<0.05) similar to what was observed in aMCI and AD patients (p<0.05). In the shared WM impairment tracts, SCD patients had FA values between the NC group and the other two patient groups. In the NC and SCD groups, the AVLT-delayed recall score correlated with higher AxD (r=−0.333, p=0.045), MD (r=−0.351, p=0.03) and RD (r=−0.353, p=0.025). In both the aMCI and AD groups the diffusion parameters were highly correlated with cognitive scores. Our study suggests that SCD patients present with widespread WM changes, which may contribute to the early memory decline they experience.
Highlights
Subjective cognitive decline (SCD), the selfperception of cognitive decline without objective evidence on standardized neuropsychological tests, is increasingly considered an at-risk stage of Alzheimer’s disease (AD), predating Mild Cognitive Impairment (MCI) [1]
The memory performance of the SCD group was intermediate to the normal controls (NC) and other two patient groups, it was still considered within the normal range
We investigated the white matter (WM) characteristics of SCD patients and found that the SCD group had detectable microstructural alterations in WM, intermediate to the NC group and the other two patient groups
Summary
Subjective cognitive decline (SCD), the selfperception of cognitive decline without objective evidence on standardized neuropsychological tests, is increasingly considered an at-risk stage of Alzheimer’s disease (AD), predating Mild Cognitive Impairment (MCI) [1]. A recent meta-analysis suggested that the annual conversion rates from SCD to MCI or AD are approximately 6.6% and 2.3%, respectively [2]. SCD may be the sole symptom for which patients seek medical advice and may be an opportunity for early intervention. Compared with MCI, SCD patients have only mild neurodegeneration and increased likelihood of successful functional compensation. Research on the SCD stage may help us better understand the early pathological mechanisms of AD, since the underlying pathological process of AD begins decades before its diagnosis. AD-related biomarkers in SCD patients would be of great value [3,4,5,6,7,8]
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