Poorer dexterity is associated with underlying Alzheimer’s disease brain pathology

Abstract

AbstractBackgroundThere has been increasing recognition for the decline of motor function in Alzheimer’s disease (AD) progression and its substantial role in disease morbidity. However, less is known about regional pathology burden—including amyloid‐β and tau protein deposition and cortical trophy—and its relationship to motor performance. Here investigate this relationship using standardized motor function assessment tools.MethodParticipants along a control‐to‐impaired continuum were enrolled in the Alzheimer’s Disease Connectome Project and underwent T1‐weighted MRI (N=206), with a subset undergoing [C‐11]PiB (N=61) and [F‐18 ]Flortaucipir PET (N=58) (Table 1) imaging for amyloid and tau pathology, respectively. T1‐weighted scans were processed using Freesurfer to estimate regional cortical thickness. [C‐11]PiB distribution volume ratios (DVR; cerebellar GM reference region) and [F‐18] Flortaucipir standardized uptake value ratios (SUVr; inferior cerebellar GM reference region) were assessed. Regions of interest (ROI) for analysis included the parahippocampal, entorhinal, motor, and frontal regions. Motor function was assessed utilizing NIH toolbox tests including the 2‐minute walking, 9‐hole pegboard dexterity, and dynamometer grip strength assessments. Motor performance was analyzed using participants uncorrected standardized scores. Scores were collected from participant‐reported dominant hand assessments. Multiple linear regression models tested relationships between AD biomarker burden and motor performance while controlling for age and sex of participants.ResultIncreased amyloid‐β (β‐0.42, p‐value: <0.05) and tau (β: ‐0.53, p‐value: <0.05) burden in primary motor cortices were associated with worse dexterity scores independent of age and sex. Grip strength did not show a significant correlation to cortical amyloid‐β (β: ‐0.14, p‐value 0.33) or tau burden (β: 0.23, p‐value: 0.36). Higher cortical thickness in primary motor regions were associated with higher dexterity (β: 0.21, p‐value <0.0001) and 2‐minute walking scores (β: 0.24, p‐value <0.001). When controlling for age and sex, grip strength predicted decreasing cortical thickness (β: 0.01, p‐value: <0.001) (Table 2).ConclusionLower dexterity performance may be driven by elevated AD pathological burden and cortical thinning in cortical motor regions. Further research into motor performance and clinical disease manifestation is needed to determine the diagnostic utility of fine motor assessment as a predictor of motor decline in individuals with Alzheimer’s disease pathology.