Distinct Patterns of Brain Atrophy in Amnestic Mild Cognitive Impairment and Motoric Cognitive Risk Syndromes.

Introduction: Motoric cognitive risk (MCR) and amnestic mild cognitive impairment (aMCI) syndromes are each reliable predictors of incident Alzheimer's disease (AD), but MCR may be a stronger predictor of vascular dementia than AD. This study contrasted cortical and hippocampal atrophy patterns in MCR and aMCI.

Methods: Cross-sectional data from 733 older adults without dementia or disability (M age = 73.6; 45% women) in the multicountry MCR consortium were examined. MCR was defined as presence of slow gait and cognitive concerns. Amnestic MCI was defined as poor episodic memory performance and cognitive concerns. Cortical thickness and hippocampal volumes were quantified from structural MRIs. Multivariate and univariate general linear models were used to examine associations between cortical thickness and hippocampal volume in MCR and aMCI, adjusting for age, sex, education, total intracranial volume, white matter lesions, and study site.

Results: The prevalence of MCR and aMCI was 7.64% and 12.96%, respectively. MCR was associated with widespread cortical atrophy, including prefrontal, insular, cingulate, motor, parietal, and temporal atrophy. aMCI was associated with hippocampal atrophy.

Conclusion: Distinct patterns of atrophy were associated with MCR and aMCI. A distributed pattern of cortical atrophy - that is more consistent with VaD or mixed dementia- was observed in MCR. A more restricted pattern of atrophy - that is more consistent with AD - was observed in aMCI. The biological underpinnings of MCR and aMCI likely differ and may require tailored interventions.