Shared and Distinct Associations of Manual Dexterity and Gross Motor Function With Brain Atrophy

Background: Poor motor function is associated with brain atrophy and cognitive impairment. Less is known about the relationship between motor domains and brain atrophy and whether associations are affected by cerebrovascular burden and/or physical activity. Methods: We analyzed data from 726 Baltimore Longitudinal Study of Aging participants (mean age 70.6 ± 10.1 years, 56% women, 27% Black), 525 of whom had repeat MRI scans over an average of 5.0 ± 2.1 years. Two motor domains, manual dexterity and gross motor, were operationalized as latent variables. Associations between the latent variables and cortical and subcortical brain volumes of interest were examined using latent growth curve modeling, adjusted for demographics, white matter hyperintensities, and physical activity. Results: Both higher manual dexterity and gross motor function were cross-sectionally associated with smaller ventricular volume and greater white matter volumes in the frontal, parietal, and temporal lobes (all p < .05). Manual dexterity was also cross-sectionally associated with parietal gray matter (B = 0.14; 95% CI: 0.05, 0.23), hippocampus (B = 0.10; 95% CI: 0.01, 0.20), postcentral gyrus (B = 0.11; 95% CI: 0.01, 0.20), and occipital white matter (B = 0.10; 95% CI: 0.01, 0.21) volumes, and gross motor function with temporal gray matter volume (B = 0.16; 95% CI: 0.05, 0.26). Longitudinally, both higher manual dexterity and gross motor function were associated with less temporal white matter and occipital gray matter atrophy (all p < .05). Manual dexterity was also associated with a slower rate of ventricular enlargement (B = −0.17; 95% CI: −0.29, −0.05) and less atrophy of occipital white matter (B = 0.39; 95% CI: 0.04, 0.71). Conclusions: Among cognitively normal middle- and older-aged adults, manual dexterity and gross motor function exhibited shared as well as distinct associations with brain atrophy over time.