Impairment of dual-task gait dynamics in older adults with mild cognitive impairment: Relationships to neuropsychological status, fitness and brain morphology

BackgroundIndividuals with Mild Cognitive Impairment (MCI) have more gait variability under dual-task conditions than cognitively healthy adults. However, characteristics associated with this susceptibility of gait to dual-task stress are unknown. MethodsTesting was performed at baseline in the Study of Mental And Resistance Training (SMART). Ninety-three adults with MCI (age 70{+/-}6.8 years; 66.6% female) performed a single- and dual-task walk (cognitive distractor=letter fluency), in random order. Linear and non-linear gait variability were measured using force-sensitive insoles. Cognitive performance during dual-tasking was assessed by the number of correct words vocalized. Cognitive function, brain Magnetic Resonance Imaging (MRI), muscle strength, aerobic capacity, body composition, physical and psychosocial function were also assessed as potential correlates of gait dynamics. ResultsGait dynamics worsened during dual-tasking, with decrements in both stride time variability (p<0.001) and detrended fluctuation analysis (DFA) (p=0.001). Lower aerobic capacity and thinner posterior cingulate cortex were associated with greater decrements in DFA (p<0.05). Smaller hippocampal volume, worse psychological well-being and poorer static balance were associated with greater decrements in stride time variability (p<0.05). By contrast, cognitive performance did not change under dual-task conditions compared to seated testing (p=0.13). ConclusionsUnder dual-task conditions, participants with MCI preserved their cognitive performance at the expense of gait stability. Decrements in dual-tasking gait were associated with lower aerobic fitness, balance, psychological well-being, and brain volume in cognitively-relevant areas of the posterior cingulate and hippocampus, all potentially modifiable characteristics. Trials of targeted interventions are needed to determine the potential plasticity of gait variability in high-risk cohorts.