title: Older adults with amnestic mild cognitive impairment exhibit exacerbated gait slowing under dual-task challenges.
abstract: 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.
authors.forename: Benjamin Y
authors.initials: BY
authors.lastname: Tseng
authors.forename: C Munro
authors.initials: CM
authors.lastname: Cullum
authors.affiliation: Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, 7232 Greenville Avenue, Dallas, TX 75231, USA. RongZhang@TexasHealth.org.
authors.forename: Rong
authors.initials: R
authors.lastname: Zhang
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D001288:Attention / Q000502:physiology; D016022:Case-Control Studies; D060825:Cognitive Dysfunction / Q000150:complications*; D003163:Competitive Behavior / Q000502:physiology*; D003430:Cross-Sectional Studies; D056344:Executive Function / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D005260:Female; D020233:Gait Disorders, Neurologic / Q000175:diagnosis* / Q000209:etiology*; D006801:Humans; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology; D008875:Middle Aged; D011930:Reaction Time / Q000502:physiology; D016138:Walking