Correlates of dual task cost of standing balance in individuals with multiple sclerosis.

Cognitive and balance dysfunction are common symptoms in individuals with multiple sclerosis (MS). Although traditionally seen as separate impairments, performing a concurrent cognitive task while maintaining an upright posture results in individuals with MS increasing their postural sway (i.e. dual task cost (DTC) of balance). However, the factors relating to this phenomenon are not clear. This investigation examined the demographic, clinical and cognitive correlates of DTC of balance in individuals with MS. Sixty-two persons with MS completed both quiet standing and dual task balance trials on a force platform. Additionally, they provided demographic information and performed clinical tests of balance, spasticity, fall risk and cognitive processing speed. Dual task cost was calculated as the percentage change in sway area from the baseline to dual task force platform conditions. Overall, there were no significant correlations between DTC of balance and any of the outcome measures in the entire sample. In contrast, postural sway in the baseline and dual task condition were found to correlate with disability, fall risk, balance performance, fatigue, cognitive processing speed and age. Secondary analysis revealed different correlates of DTC of balance in those with low versus high baseline sway. The results suggest that the change in standing balance with the simultaneous performance of cognitive task may only be informative in individuals with minimal balance dysfunction.