Associations Between the Subjective Cognitive Decline-Questionnaire's Scores, Gray Matter Volume, and Amyloid-β Levels

Background: Exploring the relationship between Alzheimer's disease (AD) biomarkers and subjective cognitive decline (SCD) is needed for better defining its clinical meaning in preclinical AD (preAD). Objective: To assess the association between the Subjective Cognitive Decline Questionnaire (SCD-Q), gray matter (GM), and cerebrospinal fluid amyloid-β (Aβ). Methods: 56 cognitively healthy older adults and their informants answered the SCD-Q. Correlations between GM and SCD-Q scores were explored using structural voxel-based morphometry models including Aβ levels. SCD-Q*Aβ vectors were calculated with higher scores reflecting higher SCD and cerebral amyloid, simultaneously. Subjects were classified according to their perception of cognitive worsening in the last two years, exploring for GM differences between-groups. Results: Higher self-reported SCD-Q scores correlated with reduced GM in the right frontal lobe and increased volumes in the occipital lobe, calcarine sulcus, fusiform gyrus, and cerebellum, while higher informant's scores correlated with increased GM in the right middle temporal gyrus. Correlations were more significant for SCD-Q language items, self-complaints, and more positive than negative correlations were found. The SCD-Q*Aβ vectors were negatively associated with GM both in self and informant's reports. Finally, lower Aβ levels related to lower GM in subjects who noticed cognitive worsening, but related to higher GM in subjects who have not noticed this decline. Conclusions: Our results suggest that SCD-Q scores relate with incipient brain changes that may be due to preAD. Independent studies are needed to confirm our observations.