Correlations of apathy and depression with postural instability in Parkinson disease.

Background: Postural instability (PI) in Parkinson's disease (PD) is associated with depression and apathy based on UPDRS scores. We sought to examine the link using more objective PI measures.

Methods: Demographic, clinical, depression and apathy data were recorded for PD patients prospectively recruited from an outpatient university movement disorders clinic. PI was objectively evaluated using the standing center of pressure sway area.

Results: Thirty-seven PD patients participated in the study. Bivariate analysis revealed that PI was significantly correlated to both apathy (p=0.018) and depression (p=0.014). Hierarchical regression revealed that apathy significantly predicted PI but depression did not significantly add to the prediction. Also, depression did not significantly predict PI and the addition of apathy did not increase this prediction.

Conclusion: Apathy and depression are both associated with objective measures of PI, and apathy appears a stronger predictor of PI than depression. Concomitant improvement in PI may be important to consider when measuring apathy or depression interventions in PD.