Mapping grey matter and cortical thickness alterations associated with subjective cognitive decline and mild cognitive impairment among rural-dwelling older adults in China: A population-based study

Abstract

Background: The structural brain alterations for subjective cognitive decline (SCD) and mild cognitive impairment (MCI) are poorly defined. We sought to characterize grey matter volume (GMV) and cortical thickness associated with SCD and MCI among rural-dwelling older adults in China.

Methods: This population-based cross-sectional study included 1072 dementia-free participants from the brain MRI sub-study of MIND-China (2018-2020). We defined MCI following the Petersen's criteria, and SCD as the self-rated Ascertain Dementia 8-item Questionnaire score ≥ 2. Data were analyzed using voxel-based morphometry (VBM), surface-based morphometry analysis (SBM), and logistic regression models.

Results: SCD was defined in 243 persons and MCI in 246 individuals. The VBM analysis showed that MCI (vs. normal cognition) was significantly associated with reduced GMV in brain regions such as the bilateral parahippocampus, bilateral hippocampus, and bilateral fusiform (P < 0.05), but SCD exhibited no significant differences with normal cognition in GMV (P > 0.05). The ROI-wise SBM analysis revealed that SCD was significantly associated with cortical thinning in the right paracentral sulcus, left caudal middle frontal gyrus, and left entorhinal cortex (P < 0.05) and that MCI was significantly associated with cortical thinning in the left temporal lobe, left frontal lobe, bilateral parietal lobe and bilateral fusiform (P < 0.05).

Conclusions: The brain regions with reduced GMV or cortical thickness in older adults gradually expand from normal cognition through SCD to MCI, suggesting that characterizing structural brain alterations may help define the cognitive spectrum at the pre-dementia phase. These findings have potential implications for understanding the neuropathological process of cognitive deterioration in aging.

Keywords: Cortical thickness; Magnetic resonance imaging; Mild cognitive impairment; Population-based study; Regional brain volume; Subjective cognitive decline.

Fig. 1

Flowchart of the study participants. Abbreviations: MIND-China, Multimodal Interventions to Delay Dementia and Disability in Rural China; MRI, magnetic resonance imaging; AD8, Ascertain Dementia 8-item Questionnaire; SCD, subjective cognitive decline; MCI, mild cognitive impairment.

Fig. 2

Comparison of whole-brain voxel-wise grey matter volume between normal cognition and mild cognitive impairment after cluster-level FWE correction. Note: Compared to individuals with normal cognition, people with mild cognitive impairment showed reduced grey matter volume mainly in the bilateral parahippocampus, bilateral hippocampus, bilateral fusiform, left precuneus, and left insula (FWE corrected p < 0.05 at cluster level). The color bar indicates the voxel-wise T-value.

Fig. 3

Comparison of whole-brain ROI-based cortical thickness between mild cognitive impairment and normal cognition, as well as between subjective cognitive decline and normal cognition after Holm-Bonferroni correction. Note: Compared to persons with normal cognition, individuals with mild cognitive impairment exhibited reduced cortical thickness mainly in the bilateral postcentral gyrus, bilateral fusiform gyrus, left superior parietal lobe, left superior frontal gyrus, left caudal middle frontal gyrus, left superior temporal gyrus and left middle temporal gyrus (Holm-Bonferroni correction, p < 0.05). People with subjective cognitive decline exhibited reduced cortical thickness mainly in the right paracentral sulcus, left caudal middle frontal gyrus, and left entorhinal cortex (Holm-Bonferroni correction, p < 0.05). The color bar indicates the P-value.