Objective: To examine the relation between brain structure and fine motor function across adult lifespan in a large cohort study.

Background: Decreased fine motor function is an important determinant of age-associated functional decline, and may be due to changes in brain structure with advancing age. Although an association between brain atrophy and decreased motor function has been reported, results from previous studies have been inconsistent, likely due to small sample sizes and technical limitations.

Method: We included 7985 participants aged between 30 and 94 years (56.5% women) from the population-based Rhineland Study, who had complete data on a digital spiral drawing test. We extracted several parameters from the spiral drawing test to assess the two most important dimensions of fine motor function, i.e. accuracy and velocity. Brain volumetric and cortical thickness measures were obtained from 3T T1 MRI scans using FreeSurfer. The relation of fine motor function (independent variable) and brain structure (outcome) was examined with multivariable regression models, while adjusting for age, sex, education, and grip strength.

Results: Decreased accuracy on the spiral drawing task was associated with smaller global brain volumes and thinner cortex of several brain regions (e.g. total brain volume: standardized β=-0.014, 95% confidence interval (CI): -0.024 to -0.003, total gray matter volume:  standardized β=-0.018，95% CI: -0.029 to -0.006, cortical thickness of precentral gyrus: standardized β= -0.051, 95% CI: -0.076 to -0.025). Although mean velocity of drawing was not significantly associated with structural brain measures, increased variability of drawing velocity was significantly associated with thinner cortex in paracentral lobule (standardized β=-0.04, 95% CI:-0.065 to -0.013) and precentral gyrus (standardized β=-0.03, 95% CI: -0.054 to -0.006).

Conclusion: Our findings indicate that fine motor function is strongly associated with both total brain and gray matter volume, as well as thickness of several critical motor regions in a large cohort of individuals from the general population.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/association-between-fine-motor-function-and-brain-structure-findings-from-the-population-based-rhineland-study/