Neuromechanisms of falls in older adults with MCI: Targeting assessment and training of reactive balance control

Mild cognitive impairment (MCI) occurs along a continuum from normal cognition to dementia and affects nearly
a quarter of individuals 70-79 years old, with the prevalence drastically increasing each decade after. Although
most older adults with MCI (OAwMCI) are independent in their daily living, they are known to have significantly
greater likelihood of falls compared to their cognitively intact counterparts. In addition to cognitive deficits,
persons with MCI can experience motor dysfunction, including deficits in gait and balance. While changes in
stance posture control and gait functionality have been thoroughly investigated in this population, reactive
balance control and protective stepping responses that are recruited to recover from unpredictable, larger
external perturbations have not yet been extensively examined. Additionally, though OAwMCI show slower
adaptation and motor learning in comparison to their healthy counterparts, it remains to be unknown whether
OAwMCI can adapt to task-specific training via repeated exposure to unpredicted perturbations as healthy
older adults (OA) do. Furthermore, it is well established that OAwMCI have worse dual-task performance
during both stance and gait. This presentation is related to impaired executive function, visuomotor function
and spatial awareness. However, dual-task performance during perturbed stance and gait in association with
increased fall-risk has not yet been investigated in OAwMCI. In addition, it is well-established that higher
cortical centers play a vital role in modulation of reactive balance control. Interestingly, in OAwMCI, the decline
in volitional balance control under sensory and cognitive challenges is corelated to an increased resting state
activation of the default mode network, reduced white matter integrity and reduced gray matter volume.
However, there is limited evidence examining the association between impaired structural integrity and
neural correlates with reactive balance control measures and resulting higher occurrence of falls in this
population. Our previous research has shown that two key variables, reactive control of stability and vertical
limb support, contribute to more than 90% of laboratory slip-falls in OA. Thus, improving these key variables
can contribute to significant reduction in fall risk in OA. However, such task-specific intervention-based studies
are lacking in the MCI population. To fill the gap in the literature, our study proposes to investigate the
differences in neuromechanics of reactive stepping responses to externally-induced balance perturbations
in OAwMCI compared to OA. Further, our study proposes to relate reactive stability control to changes in
brain structural and functional connectivity. Lastly, our study proposes to determine the effect of a novel task-
specific perturbation-based cognitive-motor intervention for enhancing fall-resisting skills in OAwMCI.

Grant Number: 5R01AG073152-04
NIH Institute/Center: NIH
Principal Investigator: Tanvi Bhatt