Title:
Cognitive and motor mechanisms underlying older adults' ability to divide attention while walking.

Abstract:
An impaired ability to allocate attention to gait during dual-task situations is a powerful predictor of falls.
The primary purpose of this study was to examine the relative contributions of participant characteristics and motor and cognitive factors to the ability to walk while performing cognitive tasks. The impact of cognitive task complexity on walking also was examined.
A cross-sectional, exploratory study design was used.
Seventy-seven community-dwelling older adults with a mean (SD) age of 75.5 (5.8) years completed comprehensive testing. Participant characteristics were assessed via questionnaires. The motor test battery included measures of strength (force-generating capacity), gait speed, and static and dynamic balance. The cognitive abilities test battery assessed psychomotor and perceptual speed, recall and working memory, verbal and spatial ability, and attention (sustained, selective, and divided). Time to walk while performing 4 cognitive tasks was measured. In addition, dual-task costs (DTCs) were calculated. Multiple hierarchical regressions explored walking under dual-task conditions.
The ability to walk and perform a simple cognitive task was explained by participant characteristics and motor factors alone, whereas walking and performing a complex cognitive task was explained by cognitive factors in addition to participant and motor factors. Regardless of the cognitive task, participants walked slower under dual-task conditions than under single-task conditions. Increased cognitive task complexity resulted in greater slowing of gait: gait DTCs were least for the simplest conditions and greatest for the complex conditions. Limitations Walking performance was characterized by a single parameter (time), whereas other spatiotemporal parameters have been related to dual-task performance. However, this type of measurement (timed performance) will be easy to implement in the clinic.
Two factors-participant characteristics and motor abilities-explained the majority of variance of walking under dual-task conditions; however, cognitive abilities also contributed significantly to the regression models. Rehabilitation focused on improving underlying balance and gait deficits, as well as specific cognitive impairments, may significantly improve walking under dual-task conditions.