Abstract
Structural brain changes underlying mild cognitive impairment (MCI) have been well-researched, but most previous studies required subjective cognitive complaints (SCC) as a diagnostic criterion, diagnosed MCI based on a single screening test or lacked analyses in relation to neuropsychological impairment. This longitudinal voxel-based morphometry study aimed to overcome these limitations: The relationship between regional gray matter (GM) atrophy and behavioral performance was investigated over the course of 3 years in individuals unaware of cognitive decline, identified as amnestic MCI based on an extensive neuropsychological test battery. Region of interest analyses revealed GM atrophy in the left amygdala, hippocampus, and parahippocampus in MCI individuals compared to normally aging participants, which was specifically related to verbal memory impairment and evident already at the first measurement point. These findings demonstrate that GM atrophy is detectable in individuals with amnestic MCI despite unawareness of beginning cognitive decline. Thus, individuals with GM atrophy in regions associated with verbal memory impairment do not necessarily need to experience SCC before meeting neuropsychological criteria for MCI. These results have important implications for future research and diagnostic procedures of MCI.
Highlights
Age-related neurodegenerative diseases such as Alzheimer’s disease (AD) impose a high social and financial burden for society that will increase in the following decades, given predictions of a 9% increase of people above 60% in 2050 (United Nations, Department of Economic and Social Affairs, 2013)
Based on the neuropsychological test battery, 16 participants were classified as mild cognitive impairment (MCI) (6 male, mean age 66.13, standard deviations (SD) 8.46 years, mean years of education 9.43, SD 1.59), and 27 participants were classified as HC (10 male, mean age 66.15, SD 6.15 years, mean years of education 10.5, SD 1.88)
The results on the neuropsychological tests for the HC and the MCI group are presented in Table 2, revealing significantly worse performance of the MCI group compared to the HC group on the total immediate recall and delayed recall subtests of the VLMT and the CERAD
Summary
Age-related neurodegenerative diseases such as Alzheimer’s disease (AD) impose a high social and financial burden for society that will increase in the following decades, given predictions of a 9% increase of people above 60% in 2050 (United Nations, Department of Economic and Social Affairs, 2013). The prevalence of AD (currently 4.7%) is predicted to increase by approximately 225% by 2050 (Prince et al, 2013). Memory disturbances constitute early symptoms of AD, and with progressing impairment, other domains become affected, including language, problem-solving, and visuospatial perception (for a review, see Dubois et al, 2016). Diagnosis is in dire need for disease prevention and the development of new treatment strategies. Detecting AD at an early time point would enable early intervention and a timely start of treatment, possibly preventing disease progression
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