Abstract
Background: Within the spectrum of Lewy body disorders (LBD), both Parkinson’s disease (PD) and dementia with Lewy bodies (DLB) are characterized by gait and balance disturbances, which become more prominent under dual-task (DT) conditions. The brain substrates underlying DT gait variations, however, remain poorly understood in LBD.
Objective: To investigate the relationship between gray matter volume loss and DT gait variations in LBD.
Methods: Seventy-nine participants including cognitively unimpaired PD, PD with mild cognitive impairment, PD with dementia (PDD), or DLB and 20 cognitively unimpaired controls were examined across a multi-site study. PDD and DLB were grouped together for analyses. Differences in gait speed between single and DT conditions were quantified by dual task cost (DTC). Cortical, subcortical, ventricle, and cerebellum brain volumes were obtained using FreeSurfer. Linear regression models were used to examine the relationship between gray matter volumes and DTC.
Results: Smaller amygdala and total cortical volumes, and larger ventricle volumes were associated with a higher DTC across LBD and cognitively unimpaired controls. No statistically significant interaction between group and brain volumes were found. Adding cognitive and motor covariates or white matter hyperintensity volumes separately to the models did not affect brain volume and DTC associations.
Conclusion: Gray matter volume loss is associated with worse DT gait performance compared to single task gait, across cognitively unimpaired controls through and the LBD spectrum. Impairment in DT gait performance may be driven by age-related cortical neurodegeneration.
Keywords: Dual task; Gait; Lewy body disorder: aging; MRI.
Plain language summary
When we walk and talk at the same time, the walking becomes slower. This slowing in walking may lead to increased risk of falls, and might be an initial sign of a serious cognitive problem. Why this slowing happens isn’t clear. We studied this phenomenon in people with Parkinson’s disease and dementia with Lewy bodies. We found that for these people, the amount of slowing while walking and counting backwards aloud at the same time was related to brain shrinkage. More slowing was related to more overall shrinkage. This might help explain why people in this clinical group slow down while doing a distracting task. Age related brain shrinkage is a key marker of this slowing while distracted.