A study of turn bias in people with idiopathic Parkinson's disease.

The objective of the study is to explore whether people with Parkinson's disease (PwPD) display a preferential turn bias dependent upon disease asymmetry, and whether specific disease features predict turn bias. PwPD and age-matched controls were instructed to walk on an instrumented gait mat making "normal" turns. Trials were analyzed using Proto Kinetics Movement Analysis Software (PKMAS) and time-locked video recordings to obtain turn directionality and spatiotemporal turn measures. Turn bias was estimated using previously defined formulas. Seventy-two PwPD and 28 controls were included. One hundred percent of controls and 85% of PwPD had left turn bias. Turn bias was not significantly associated with age, gender, handedness, disease asymmetry, cognition, or disease severity. The Freezing of Gait Questionnaire (FOGQ) questions 5 and 6 showed linear-by-linear association with turn bias. In binary logistic and ordinal regression models, FOGQ question 6 (average duration of turn freezing) and turn width were predictive of turn bias. Rightward turns had greater frequency of freezing episodes. Turn bias in our PwPD cohort does not appear related to disease asymmetry or other disease features, except gait freezing. Whether freezing severity on turning leads to non-left turn bias or vice versa requires more focused studies. Physical therapy interventions targeting turning direction in PwPD could reduce freezing severity.