Distinct Patterns of Brain Atrophy in MCR and amnestic MCI pre‐dementia syndromes

Abstract

AbstractBackgroundBoth amnestic Mild Cognitive Impairment (aMCI) and the Motoric Cognitive Risk (MCR) syndrome are reliable predictors of Alzheimer’s Disease (AD). There is also some evidence for that MCR is a stronger predictor of vascular dementia (VaD) than AD. The current study directly compared cortical and hippocampal atrophy patterns in MCR and aMCI to inform the development of interventions targeted to these pre‐dementia syndromes. We hypothesized that MCR would be associated with a widespread pattern of cortical atrophy while aMCI would be associated with atrophy restricted to hippocampal and neighboring temporal regions.MethodCross‐sectional data from 733 older adults without dementia and functional disabilities from the MCR‐consortium were examined. MCR was operationalized as slow gait and subjective cognitive complaint, using previously established cohort‐specific criteria. aMCI was operationalized as 1.5 standard deviation or more below standardized performance on episodic memory measures. FreeSurfer v6.0 was applied to T‐1 weighted MRIs to examine cortical thickness and hippocampal atrophy patterns in MCR and aMCI relative to those without MCR and aMCI, respectively. Separate general linear models (GLMs) examined the associations between overall and regional cortical thickness, hippocampal volume, and MCR and aMCI. All GLMs were adjusted for age, sex, education, total intracranial volume, white matter lesion burden, and study site.ResultThe mean age of the sample was 74.4 years (45.4% women). The prevalence of MCR and aMCI was 7.6% and 2.6 %, respectively. Both MCR and aMCI was associated with overall cortical atrophy. Yet, while MCR was associated widespread cortical atrophy – that included prefrontal, insular, cingulate, motor, parietal and temporal regions – aMCI was associated with a restricted pattern of atrophy that primarily included temporal and hippocampal regions.ConclusionThis study revealed distinct patterns of atrophy in older adults with MCR and aMCI pre‐dementia syndromes. A widespread pattern of cortical atrophy – that is more consistent with VaD or mixed dementia than AD – was observed in MCR. A more restricted pattern of atrophy – that is more consistent with AD than VaD or mixed dementia – was observed in aMCI. Thus, the biological underpinnings of MCR and aMCI likely differ, and may require tailored interventions.