Background: With age, performance of motor tasks becomes more reliant on cognitive resources to compensate
for the structural and functional declines in the motor control regions in the brain. We hypothesized that participants with
amnestic mild cognitive impairment (aMCI) are more prone to motor dysfunctions than cognitively normal older adults
under dual-task conditions where competitive demands challenge cognitive functions while performing a motor task simultaneously.
Methods: Sixteen aMCI participants (females=9, age=64±5yrs, clinical dementia rating score=0.5) and 10
age- and education-matched cognitively normal adults (females=5, age=62±6yrs) participated. Using a 10-meter-walk test
(10MW), gait velocity was recorded at baseline and under 4 different dual-task (DT) conditions designed to challenge
working memory, executive function, and episodic memory. Specifically, DT1: verbal fluency; DT2: 5-digit backward
span; DT3: serial-7 subtraction; and DT4: 3-item delayed recall. Physical function was measured by Timed Up-and-Go
(TUG), simple reaction time (RT) to a free-falling yardstick, and functional reach (FR). Results: No difference was found
in physical functions, aerobic fitness, and exercise cardiopulmonary responses between aMCI participants and controls.
However, aMCI participants showed more pronounced gait slowing from baseline when compared to the controls
(p<0.05; p=0.001; p<0.001; p<0.001, respectively). Conclusions: Our finding supports the theory of shared resource of
motor and cognitive control. Participants with aMCI manifested more gait slowing than cognitively-normal older adults
under DT conditions, with the largest differences during tests of working and episodic memory. The outcome of dual-task
assessment shows promise as a potential marker for detection of aMCI and early Alzheimer disease.