Mild cognitive disorders are associated with different patterns of brain asymmetry than normal aging: the PATH through life study

Abstract

Background and Purpose: Defining how brain structures differ in pre-clinical dementia is important to better understand the pathological processes involved and to inform clinical practice. The aim of this study was to identify significant brain correlates (volume and asymmetry in volume) of mild cognitive disorders when compared to normal controls in a large community-based sample of young-old individuals who were assessed for cognitive impairment. Methods: Cortical and sub-cortical volumes were measured using a semi-automated method in 398 participants aged 64–70 years who were selected from a larger randomly sampled cohort and who agreed to undergo an MRI scan. Diagnoses were reached based on established protocols for MCI and a more inclusive category of any Mild Cognitive Disorder (any-MCD: which includes AAMI, AACD, OCD, MNC, CDR, MCI). Logistic regression analyses were used to assess the relationship between volume and asymmetry of theoretically relevant cerebral structures (predictors) and MCI or any-MCD while controlling for age, sex, and intra-cranial volume. Results: The main correlates of cognitive impairment assessed in multivariate analyses were hippocampal asymmetry (more to left, MCI: OR 0.83, 95%CI 0.71–0.96, p = 0.013; MCD: OR 0.86, 95%CI 0.77–0.97, p = 0.011), lateral ventricle asymmetry (more to left, MCI: OR 0.95, 95%CI 0.91–0.99, p = 0.009; MCD: OR 0.95, 95%CI 0.92–0.98, p = 0.004), and cerebellar cortex asymmetry (more to right, MCI: OR 1.51, 95%CI 1.13–2.01, p = 0.005). Conclusions: In this population-based cohort stronger associations were found between asymmetry measures, rather than raw volumes in cerebral structures, and mild cognitive disorders.

Hippocampal Atrophy Is Associated with Subjective Memory Decline: The PATH Through Life Study

“…Such effects should be further investigated in future studies because the left and right hemispheres have been reported to differ in their vulnerability to AD neurodegenerative processes, which tend to start earlier and progress faster in the left hemisphere. 37,38 The prevalence of SMD in the present sample was similar to rates reported in the literature for epidemiological samples with 23% reporting SMD at baseline and 18% at follow-up. 3,23 Because individuals with dementia, MCI, or neurological disorder were excluded, SMD was not associated with pre-existing clinical disorders.…”

Low Plasma ApoE Levels Are Associated with Smaller Hippocampal Size in the Alzheimer's Disease Neuroimaging Initiative Cohort

“…This phenomenon could have theoretically impacted our results, even though our hippocampal indices were derived from automated segmentation, since the initial training set was developed through manual tracing. Although these results remain incompletely understood, they raise the possibility that the interactions between hippocampal volume and other AD biomarkers and risk factors may not always be bilaterally symmetric, particularly since greater hemispheric asymmetry in hippocampal volumes is associated with a higher likelihood of cognitive impairment [47]. …”

Assessing Corpus Callosum Changes in Alzheimer's Disease: Comparison between Tract-Based Spatial Statistics and Atlas-Based Tractography

“…These fibers (CC6L) are indeed originating from the left temporo-parietal GM, which is primarily affected in the early stages of AD [21], [36], [52], [53].…”