Brain structural asymmetry associated with cognitive impairment in community-dwelling older adults

Identifying factors that contribute to cognitive impairment is crucial for the risk assessment of dementia. In this cross-sectional study, we aimed to clarify the relationship between structural brain asymmetry and cognitive impairments in older adults. This study included data from 1047 eligible community-dwelling older adults (aged 70.0 ± 6.3 years). We analyzed the association between the cognitive function tests (memory [word-list memory], attention [Trail Making Test Part A], and executive function [Trail Making Test Part B]). All tests used established standardized thresholds in a population-based cohort. Herein, we used 1.5 SD below the mean as criteria for cognitive impairment. Brain volumes were processed with FreeSurfer 6.0, analyzing the hippocampus, amygdala, and temporal lobe for memory information processing, while the dorsolateral prefrontal cortex, inferior frontal gyrus, anterior cingulate cortex, inferior parietal lobule, and thalamus were analyzed for attention and executive functions. Brain structural asymmetry was evaluated using the asymmetry index: (|R-L|) / (R + L) × 100. Logistic regression analysis was performed to assess the relationship between cognitive impairment and the brain asymmetry index. We found that the structural asymmetry of the anterior cingulate cortex was significantly associated with attentional impairment (Odds ratio = 1.37, 95 %CI = 1.01-1.85, p = 0.04). Structural asymmetry of the dorsolateral prefrontal cortex was tended to associated with executive function impairment (Odds ratio = 1.22, 95 %CI = 0.99-1.51, p = 0.06). These results suggest that structural asymmetry was associated factor for detecting attentional impairment and executive function impairment in the anterior cingulate cortex and dorsolateral prefrontal cortex.