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The interacting effects of cognitive demand and recovery of postural stability in balance-impaired elderly persons.

BACKGROUND
Although postural recovery is attentionally demanding in healthy elderly persons, an inability to recover balance due to competition for attentional resources between the postural system and a second task could contribute to falls in older adults with poor balance. This study examined the attentional demands of balance recovery from a mild postural disturbance in balance-impaired elderly persons. A second purpose of this research was to determine the effect of performing a cognitive task on the recovery of balance in balance-impaired elderly persons.


METHODS
Fifteen healthy older adults and 13 older adults with clinical balance impairment were exposed to balance disturbances by means of sudden movement of a platform on which they stood. A dual-task paradigm where postural recovery served as the primary task and verbal reaction time to auditory tones served as the secondary task was used to assess attentional demand. To determine the effect of the cognitive task on postural recovery, kinetic, kinematic, and neuromuscular measures of a feet-in-place response were investigated.


RESULTS
Balance recovery using a feet-in-place response was attentionally demanding in both groups of older adults and was more demanding in balance-impaired than in healthy elderly persons. With the concurrent performance of a cognitive task, balance-impaired elderly persons took longer to stabilize their center of pressure and regain balance than in a single task, while healthy elderly persons showed no change between conditions. In addition, only balance-impaired elderly individuals had a greater center-of-pressure resultant velocity during recovery in a dual-task compared with a single-task situation.


CONCLUSIONS
The ability to recover balance using a feet-in-place response was more attentionally demanding in balance-impaired than in healthy elderly persons. The recovery of balance was also slower and less efficient in balance-impaired elderly persons when simultaneously performing a cognitive task, whereas the ability of healthy elderly individuals to recover was not influenced by concurrent task demands. This suggests that dual-task performance may contribute to postural instability and falls in balance-impaired elderly individuals.