The influence of dopaminergic medication on balance automaticity in Parkinson's disease.

BACKGROUND

Studies have shown that dual-task standing balance in Parkinson's disease (PD) is significantly diminished. Additionally, it is well accepted that dopaminergic medication improves dynamic balance (Berg Balance Scale, mini-BESTest), but standing balance (force platform posturography) may suffer. What remains unknown is how dopaminergic medication influences standing balance automaticity in PD.

RESEARCH QUESTION

Does dopaminergic medication improve standing balance automaticity during a phoneme monitoring dual-task in PD?

METHODS

This was a cross-sectional study. Sixteen subjects with PD completed single- and dual-task standing with eyes open and eyes closed for 3 min each in off and on medication states. 95% confidence ellipse area, anterior-posterior sway velocity, medial-lateral sway velocity, and integrated time to boundary were calculated. Data were analyzed with a repeated measures ANOVA.

RESULTS

Dopaminergic medication significantly increased ellipse area (p =  0.002) and decreased the performance on the secondary task (p =  0.004). Different eyes conditions (open vs. closed) significantly increased both sway velocities (anterior-posterior = p <  0.001, medial-lateral = p <  0.001), and increased integrated time to boundary (p <  0.001). There were also task by eyes condition interaction effects for anterior-posterior velocity and integrated time to boundary (p =  0.015 and p =  0.009, respectively). Increases in sway velocity and integrated time to boundary seen in the eyes condition and interaction effects are traditionally interpreted as poorer balance performance. However, in the context of stability/maneuverability tradeoff, the changes may indicate an increase in freedom of movement instead of a decrease in stability.

SIGNIFICANCE

The data did not support a medication-induced improvement in automaticity, as measured by significant medication by task interactions. An alternate interpretation for medication-induced balance changes in PD includes an increase in maneuverability without sacrificing stability after taking dopaminergic medication.